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13.2. Lista funcțiilor

The functions, operators and variables available in QGIS are listed below, grouped by categories.

13.2.1. Funcții de Agregare

This group contains functions which aggregate values over layers and fields.

13.2.1.1. aggregate

Returns an aggregate value calculated using features from another layer.

Sintaxă

aggregate(layer, aggregate, expression, [filter], [concatenator=»»], [order_by])

[] marks optional arguments

Argumente

  • layer - a string, representing either a layer name or layer ID

  • aggregate - a string corresponding to the aggregate to calculate. Valid options are:

    • count

    • count_distinct

    • count_missing

    • min

    • max

    • sum

    • mean

    • median

    • stdev

    • stdevsample

    • range

    • minority

    • majority

    • q1: first quartile

    • q3: third quartile

    • iqr: inter quartile range

    • min_length: minimum string length

    • max_length: maximum string length

    • concatenate: join strings with a concatenator

    • concatenate_unique: join unique strings with a concatenator

    • collect: create an aggregated multipart geometry

    • array_agg: create an array of aggregated values

  • expression - sub expression or field name to aggregate

  • filter - optional filter expression to limit the features used for calculating the aggregate. Fields and geometry are from the features on the joined layer. The source feature can be accessed with the variable @parent.

  • concatenator - optional string to use to join values for «concatenate» and «concatenate_unique» aggregates

  • order_by - optional filter expression to order the features used for calculating the aggregate. Fields and geometry are from the features on the joined layer. By default, the features will be returned in an unspecified order.

Exemple

  • aggregate(layer:='rail_stations',aggregate:='sum',expression:="passengers") → sum of all values from the passengers field in the rail_stations layer

  • aggregate('rail_stations','sum', "passengers"/7) → calculates a daily average of „passengers” by dividing the „passengers” field by 7 before summing the values

  • aggregate(layer:='rail_stations',aggregate:='sum',expression:="passengers",filter:="class">3) → sums up all values from the „passengers” field from features where the „class” attribute is greater than 3 only

  • aggregate(layer:='rail_stations',aggregate:='concatenate', expression:="name", concatenator:=',') → comma separated list of the name field for all features in the rail_stations layer

  • aggregate(layer:='countries', aggregate:='max', expression:="code", filter:=intersects( @geometry, geometry(@parent) ) ) → The country code of an intersecting country on the layer «countries»

  • aggregate(layer:='rail_stations',aggregate:='sum',expression:="passengers",filter:=contains( @atlas_geometry, @geometry ) ) → sum of all values from the passengers field in the rail_stations within the current atlas feature

  • aggregate(layer:='rail_stations', aggregate:='collect', expression:=centroid(@geometry), filter:="region_name" = attribute(@parent,'name') ) → aggregates centroid geometries of the rail_stations of the same region as current feature

13.2.1.2. array_agg

Returns an array of aggregated values from a field or expression.

Sintaxă

array_agg(expression, [group_by], [filter], [order_by])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

  • order_by - optional expression to use to order features used to calculate aggregate. By default, the features will be returned in an unspecified order.

Exemple

  • array_agg("name",group_by:="state") → list of name values, grouped by state field

13.2.1.3. collect

Returns the multipart geometry of aggregated geometries from an expression

Sintaxă

collect(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - geometry expression to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • collect( @geometry ) → multipart geometry of aggregated geometries

  • collect( centroid(@geometry), group_by:="region", filter:= "use" = 'civilian' ) → aggregated centroids of the civilian features based on their region value

13.2.1.4. concatenate

Returns all aggregated strings from a field or expression joined by a delimiter.

Sintaxă

concatenate(expression, [group_by], [filter], [concatenator], [order_by])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

  • concatenator - optional string to use to join values. Empty by default.

  • order_by - optional expression to use to order features used to calculate aggregate. By default, the features will be returned in an unspecified order.

Exemple

  • concatenate("town_name",group_by:="state",concatenator:=',') → comma separated list of town_names, grouped by state field

13.2.1.5. concatenate_unique

Returns all unique strings from a field or expression joined by a delimiter.

Sintaxă

concatenate_unique(expression, [group_by], [filter], [concatenator], [order_by])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

  • concatenator - optional string to use to join values. Empty by default.

  • order_by - optional expression to use to order features used to calculate aggregate. By default, the features will be returned in an unspecified order.

Exemple

  • concatenate_unique("town_name",group_by:="state",concatenator:=',') → comma separated list of unique town_names, grouped by state field

13.2.1.6. count

Returns the count of matching features.

Sintaxă

count(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • count("stations",group_by:="state") → count of stations, grouped by state field

13.2.1.7. count_distinct

Returns the count of distinct values.

Sintaxă

count_distinct(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • count_distinct("stations",group_by:="state") → count of distinct stations values, grouped by state field

13.2.1.8. count_missing

Returns the count of missing (NULL) values.

Sintaxă

count_missing(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • count_missing("stations",group_by:="state") → count of missing (NULL) station values, grouped by state field

13.2.1.9. iqr

Returns the calculated inter quartile range from a field or expression.

Sintaxă

iqr(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • iqr("population",group_by:="state") → inter quartile range of population value, grouped by state field

13.2.1.10. majority

Returns the aggregate majority of values (most commonly occurring value) from a field or expression.

Sintaxă

majority(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • majority("class",group_by:="state") → most commonly occurring class value, grouped by state field

13.2.1.11. max_length

Returns the maximum length of strings from a field or expression.

Sintaxă

max_length(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • max_length("town_name",group_by:="state") → maximum length of town_name, grouped by state field

13.2.1.12. maximum

Returns the aggregate maximum value from a field or expression.

Sintaxă

maximum(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • maximum("population",group_by:="state") → maximum population value, grouped by state field

13.2.1.13. mean

Returns the aggregate mean value from a field or expression.

Sintaxă

mean(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • mean("population",group_by:="state") → mean population value, grouped by state field

13.2.1.14. median

Returns the aggregate median value from a field or expression.

Sintaxă

median(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • median("population",group_by:="state") → median population value, grouped by state field

13.2.1.15. min_length

Returns the minimum length of strings from a field or expression.

Sintaxă

min_length(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • min_length("town_name",group_by:="state") → minimum length of town_name, grouped by state field

13.2.1.16. minimum

Returns the aggregate minimum value from a field or expression.

Sintaxă

minimum(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • minimum("population",group_by:="state") → minimum population value, grouped by state field

13.2.1.17. minority

Returns the aggregate minority of values (least occurring value) from a field or expression.

Sintaxă

minority(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • minority("class",group_by:="state") → least occurring class value, grouped by state field

13.2.1.18. q1

Returns the calculated first quartile from a field or expression.

Sintaxă

q1(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • q1("population",group_by:="state") → first quartile of population value, grouped by state field

13.2.1.19. q3

Returns the calculated third quartile from a field or expression.

Sintaxă

q3(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • q3("population",group_by:="state") → third quartile of population value, grouped by state field

13.2.1.20. range

Returns the aggregate range of values (maximum - minimum) from a field or expression.

Sintaxă

range(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • range("population",group_by:="state") → range of population values, grouped by state field

13.2.1.21. relation_aggregate

Returns an aggregate value calculated using all matching child features from a layer relation.

Sintaxă

relation_aggregate(relation, aggregate, expression, [concatenator=»»], [order_by])

[] marks optional arguments

Argumente

  • relation - a string, representing a relation ID

  • aggregate - a string corresponding to the aggregate to calculate. Valid options are:

    • count

    • count_distinct

    • count_missing

    • min

    • max

    • sum

    • mean

    • median

    • stdev

    • stdevsample

    • range

    • minority

    • majority

    • q1: first quartile

    • q3: third quartile

    • iqr: inter quartile range

    • min_length: minimum string length

    • max_length: maximum string length

    • concatenate: join strings with a concatenator

    • concatenate_unique: join unique strings with a concatenator

    • collect: create an aggregated multipart geometry

    • array_agg: create an array of aggregated values

  • expression - sub expression or field name to aggregate

  • concatenator - optional string to use to join values for «concatenate» aggregate

  • order_by - optional expression to order the features used for calculating the aggregate. Fields and geometry are from the features on the joined layer. By default, the features will be returned in an unspecified order.

Exemple

  • relation_aggregate(relation:='my_relation',aggregate:='mean',expression:="passengers") → mean value of all matching child features using the «my_relation» relation

  • relation_aggregate('my_relation','sum', "passengers"/7) → sum of the passengers field divided by 7 for all matching child features using the «my_relation» relation

  • relation_aggregate('my_relation','concatenate', "towns", concatenator:=',') → comma separated list of the towns field for all matching child features using the «my_relation» relation

  • relation_aggregate('my_relation','array_agg', "id") → array of the id field from all matching child features using the «my_relation» relation

Mai multe detalii: Setting relations between multiple layers

13.2.1.22. stdev

Returns the aggregate standard deviation value from a field or expression.

Sintaxă

stdev(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • stdev("population",group_by:="state") → standard deviation of population value, grouped by state field

13.2.1.23. sum

Returns the aggregate summed value from a field or expression.

Sintaxă

sum(expression, [group_by], [filter])

[] marks optional arguments

Argumente

  • expression - sub expression of field to aggregate

  • group_by - optional expression to use to group aggregate calculations

  • filter - optional expression to use to filter features used to calculate aggregate

Exemple

  • sum("population",group_by:="state") → summed population value, grouped by state field

13.2.2. Array Functions

This group contains functions to create and manipulate arrays (also known as list data structures). The order of values within the array matters, unlike the «map» data structure, where the order of key-value pairs is irrelevant and values are identified by their keys.

13.2.2.1. array

Returns an array containing all the values passed as parameter.

Sintaxă

array(value1, value2, …)

Argumente

  • value - o valoare

Exemple

  • array(2,10) → [ 2, 10 ]

  • array(2,10)[0] → 2

13.2.2.2. array_all

Returns TRUE if an array contains all the values of a given array.

Sintaxă

array_all(array_a, array_b)

Argumente

  • array_a - an array

  • array_b - the array of values to search

Exemple

  • array_all(array(1,2,3),array(2,3)) → TRUE

  • array_all(array(1,2,3),array(1,2,4)) → FALSE

13.2.2.3. array_append

Returns an array with the given value added at the end.

Sintaxă

array_append(array, value)

Argumente

  • array - an array

  • value - valoarea de adăugat

Exemple

  • array_append(array(1,2,3),4) → [ 1, 2, 3, 4 ]

13.2.2.4. array_cat

Returns an array containing all the given arrays concatenated.

Sintaxă

array_cat(array1, array2, …)

Argumente

  • array - an array

Exemple

  • array_cat(array(1,2),array(2,3)) → [ 1, 2, 2, 3 ]

13.2.2.5. array_contains

Returns TRUE if an array contains the given value.

Sintaxă

array_contains(array, value)

Argumente

  • array - an array

  • value - the value to search

Exemple

  • array_contains(array(1,2,3),2) → TRUE

13.2.2.6. array_count

Counts the number of occurrences of a given value in an array.

Sintaxă

array_count(array, value)

Argumente

  • array - an array

  • value - the value to count

Exemple

  • array_count(array('a', 'b', 'c', 'b'), 'b') → 2

13.2.2.7. array_distinct

Returns an array containing distinct values of the given array.

Sintaxă

array_distinct(array)

Argumente

  • array - an array

Exemple

  • array_distinct(array(1,2,3,2,1)) → [ 1, 2, 3 ]

13.2.2.8. array_filter

Returns an array with only the items for which the expression evaluates to true.

Sintaxă

array_filter(array, expression, [limit=0])

[] marks optional arguments

Argumente

  • array - an array

  • expression - an expression to evaluate on each item. The variable @element will be replaced by the current value.

  • limit - maximum number of elements to be returned. Use 0 to return all values.

Exemple

  • array_filter(array(1,2,3),@element < 3) → [ 1, 2 ]

  • array_filter(array(1,2,3),@element < 3, 1) → [ 1 ]

13.2.2.9. array_find

Returns the lowest index (0 for the first one) of a value within an array. Returns -1 if the value is not found.

Sintaxă

array_find(array, value)

Argumente

  • array - an array

  • value - the value to search

Exemple

  • array_find(array('a', 'b', 'c'), 'b') → 1

  • array_find(array('a', 'b', 'c', 'b'), 'b') → 1

13.2.2.10. array_first

Returns the first value of an array.

Sintaxă

array_first(array)

Argumente

  • array - an array

Exemple

  • array_first(array('a','b','c')) → «a»

13.2.2.11. array_foreach

Returns an array with the given expression evaluated on each item.

Sintaxă

array_foreach(array, expression)

Argumente

  • array - an array

  • expression - an expression to evaluate on each item. The variable @element will be replaced by the current value.

Exemple

  • array_foreach(array('a','b','c'),upper(@element)) → [ «A», «B», «C» ]

  • array_foreach(array(1,2,3),@element + 10) → [ 11, 12, 13 ]

13.2.2.12. array_get

Returns the Nth value (0 for the first one) or the last -Nth value (-1 for the last one) of an array.

Sintaxă

array_get(array, pos)

Argumente

  • array - an array

  • pos - the index to get (0 based)

Exemple

  • array_get(array('a','b','c'),1) → «b»

  • array_get(array('a','b','c'),-1) → «c»

Sugestie

You can also use the index operator ([]) to get a value from an array.

13.2.2.13. array_insert

Returns an array with the given value added at the given position.

Sintaxă

array_insert(array, pos, value)

Argumente

  • array - an array

  • pos - the position where to add (0 based)

  • value - valoarea de adăugat

Exemple

  • array_insert(array(1,2,3),1,100) → [ 1, 100, 2, 3 ]

13.2.2.14. array_intersect

Returns TRUE if at least one element of array1 exists in array2.

Sintaxă

array_intersect(array1, array2)

Argumente

  • array1 - an array

  • array2 - another array

Exemple

  • array_intersect(array(1,2,3,4),array(4,0,2,5)) → TRUE

13.2.2.15. array_last

Returns the last value of an array.

Sintaxă

array_last(array)

Argumente

  • array - an array

Exemple

  • array_last(array('a','b','c')) → «c»

13.2.2.16. array_length

Returns the number of elements of an array.

Sintaxă

array_length(array)

Argumente

  • array - an array

Exemple

  • array_length(array(1,2,3)) → 3

13.2.2.17. array_majority

Returns the most common values in an array.

Sintaxă

array_majority(array, [option=»all»])

[] marks optional arguments

Argumente

  • array - an array

  • option=»all» - a string specifying the return values handling. Valid options are:

    • all: Default, all most common values are returned in an array.

    • any: Returns one of the most common values.

    • median: Returns the median of the most common values. Non arithmetic values are ignored.

    • real_majority: Returns the value which occurs more than half the size of the array.

Exemple

  • array_majority(array(0,1,42,42,43), 'all') → [ 42 ]

  • array_majority(array(0,1,42,42,43,1), 'all') → [ 42, 1 ]

  • array_majority(array(0,1,42,42,43,1), 'any') → 1 or 42

  • array_majority(array(0,1,1,2,2), 'median') → 1.5

  • array_majority(array(0,1,42,42,43), 'real_majority') → NULL

  • array_majority(array(0,1,42,42,43,42), 'real_majority') → NULL

  • array_majority(array(0,1,42,42,43,42,42), 'real_majority') → 42

13.2.2.18. array_max

Returns the maximum value of an array.

Sintaxă

array_max(array)

Argumente

  • array - an array

Exemple

  • array_max(array(0,42,4,2)) → 42

13.2.2.19. array_mean

Returns the mean of arithmetic values in an array. Non numeric values in the array are ignored.

Sintaxă

array_mean(array)

Argumente

  • array - an array

Exemple

  • array_mean(array(0,1,7,66.6,135.4)) → 42

  • array_mean(array(0,84,'a','b','c')) → 42

13.2.2.20. array_median

Returns the median of arithmetic values in an array. Non arithmetic values in the array are ignored.

Sintaxă

array_median(array)

Argumente

  • array - an array

Exemple

  • array_median(array(0,1,42,42,43)) → 42

  • array_median(array(0,1,2,42,'a','b')) → 1.5

13.2.2.21. array_min

Returns the minimum value of an array.

Sintaxă

array_min(array)

Argumente

  • array - an array

Exemple

  • array_min(array(43,42,54)) → 42

13.2.2.22. array_minority

Returns the less common values in an array.

Sintaxă

array_minority(array, [option=»all»])

[] marks optional arguments

Argumente

  • array - an array

  • option=»all» - a string specifying the return values handling. Valid options are:

    • all: Default, all less common values are returned in an array.

    • any: Returns one of the less common values.

    • median: Returns the median of the less common values. Non arithmetic values are ignored.

    • real_minority: Returns values which occur less than half the size of the array.

Exemple

  • array_minority(array(0,42,42), 'all') → [ 0 ]

  • array_minority(array(0,1,42,42), 'all') → [ 0, 1 ]

  • array_minority(array(0,1,42,42,43,1), 'any') → 0 or 43

  • array_minority(array(1,2,3,3), 'median') → 1.5

  • array_minority(array(0,1,42,42,43), 'real_minority') → [ 42, 43, 0, 1 ]

  • array_minority(array(0,1,42,42,43,42), 'real_minority') → [ 42, 43, 0, 1 ]

  • array_minority(array(0,1,42,42,43,42,42), 'real_minority') → [ 43, 0, 1 ]

13.2.2.23. array_prepend

Returns an array with the given value added at the beginning.

Sintaxă

array_prepend(array, value)

Argumente

  • array - an array

  • value - valoarea de adăugat

Exemple

  • array_prepend(array(1,2,3),0) → [ 0, 1, 2, 3 ]

13.2.2.24. array_prioritize

Returns an array sorted using the ordering specified in another array. Values which are present in the first array but are missing from the second array will be added to the end of the result.

Sintaxă

array_prioritize(array, array_prioritize)

Argumente

  • array - an array

  • array_prioritize - an array with values ordered by priority

Exemple

  • array_prioritize(array(1, 8, 2, 5), array(5, 4, 2, 1, 3, 8)) → [ 5, 2, 1, 8 ]

  • array_prioritize(array(5, 4, 2, 1, 3, 8), array(1, 8, 6, 5)) → [ 1, 8, 5, 4, 2, 3 ]

13.2.2.25. array_remove_all

Returns an array with all the entries of the given value removed.

Sintaxă

array_remove_all(array, value)

Argumente

  • array - an array

  • value - the values to remove

Exemple

  • array_remove_all(array('a','b','c','b'),'b') → [ «a», «c» ]

13.2.2.26. array_remove_at

Returns an array with the item at the given index removed. Supports positive (0 for the first element) and negative (the last -Nth value, -1 for the last element) index.

Sintaxă

array_remove_at(array, pos)

Argumente

  • array - an array

  • pos - the position to remove (0 based)

Exemple

  • array_remove_at(array(1, 2, 3), 1) → [1, 3 ]

  • array_remove_at(array(1, 2, 3), -1) → [1, 2 ]

13.2.2.27. array_replace

Returns an array with the supplied value, array, or map of values replaced.

Value & array variant

Returns an array with the supplied value or array of values replaced by another value or an array of values.

Sintaxă

array_replace(array, before, after)

Argumente

  • array - the input array

  • before - the value or array of values to replace

  • after - the value or array of values to use as a replacement

Exemple

  • array_replace(array('QGIS','SHOULD','ROCK'),'SHOULD','DOES') → [ «QGIS», «DOES», «ROCK» ]

  • array_replace(array(3,2,1),array(1,2,3),array(7,8,9)) → [ 9, 8, 7 ]

  • array_replace(array('Q','G','I','S'),array('Q','S'),'-') → [ «-», «G», «I», «-» ]

Map variant

Returns an array with the supplied map keys replaced by their paired values.

Sintaxă

array_replace(array, map)

Argumente

  • array - the input array

  • map - the map containing keys and values

Exemple

  • array_replace(array('APP', 'SHOULD', 'ROCK'),map('APP','QGIS','SHOULD','DOES')) → [ «QGIS», «DOES», «ROCK» ]

13.2.2.28. array_reverse

Returns the given array with array values in reversed order.

Sintaxă

array_reverse(array)

Argumente

  • array - an array

Exemple

  • array_reverse(array(2,4,0,10)) → [ 10, 0, 4, 2 ]

13.2.2.29. array_slice

Returns a portion of the array. The slice is defined by the start_pos and end_pos arguments.

Sintaxă

array_slice(array, start_pos, end_pos)

Argumente

  • array - an array

  • start_pos - the index of the start position of the slice (0 based). The start_pos index is included in the slice. If you use a negative start_pos, the index is counted from the end of the list (-1 based).

  • end_pos - the index of the end position of the slice (0 based). The end_pos index is included in the slice. If you use a negative end_pos, the index is counted from the end of the list (-1 based).

Exemple

  • array_slice(array(1,2,3,4,5),0,3) → [ 1, 2, 3, 4 ]

  • array_slice(array(1,2,3,4,5),0,-1) → [ 1, 2, 3, 4, 5 ]

  • array_slice(array(1,2,3,4,5),-5,-1) → [ 1, 2, 3, 4, 5 ]

  • array_slice(array(1,2,3,4,5),0,0) → [ 1 ]

  • array_slice(array(1,2,3,4,5),-2,-1) → [ 4, 5 ]

  • array_slice(array(1,2,3,4,5),-1,-1) → [ 5 ]

  • array_slice(array('Dufour','Valmiera','Chugiak','Brighton'),1,2) → [ «Valmiera», «Chugiak» ]

  • array_slice(array('Dufour','Valmiera','Chugiak','Brighton'),-2,-1) → [ «Chugiak», «Brighton» ]

13.2.2.30. array_sort

Returns the provided array with its elements sorted.

Sintaxă

array_sort(array, [ascending=true])

[] marks optional arguments

Argumente

  • array - an array

  • ascending - set this parameter to false to sort the array in descending order

Exemple

  • array_sort(array(3,2,1)) → [ 1, 2, 3 ]

13.2.2.31. array_sum

Returns the sum of arithmetic values in an array. Non numeric values in the array are ignored.

Sintaxă

array_sum(array)

Argumente

  • array - an array

Exemple

  • array_sum(array(0,1,39.4,1.6,'a')) → 42.0

13.2.2.32. array_to_string

Concatenates array elements into a string separated by a delimiter and using optional string for empty values.

Sintaxă

array_to_string(array, [delimiter=»,»], [empty_value=»»])

[] marks optional arguments

Argumente

  • array - the input array

  • delimiter - the string delimiter used to separate concatenated array elements

  • empty_value - the optional string to use as replacement for empty (zero length) matches

Exemple

  • array_to_string(array('1','2','3')) → «1,2,3»

  • array_to_string(array(1,2,3),'-') → «1-2-3»

  • array_to_string(array('1','','3'),',','0') → «1,0,3»

13.2.2.33. generate_series

Creează o matrice care conține o secvență de numere.

Sintaxă

generate_series(start, stop, [step=1])

[] marks optional arguments

Argumente

  • start - prima valoare a secvenței

  • stop - valoare care încheie secvența o dată atinsă

  • pas - valoare folosită ca increment între valori

Exemple

  • generate_series(1,5) → [ 1, 2, 3, 4, 5 ]

  • generate_series(5,1,-1) → [ 5, 4, 3, 2, 1 ]

13.2.2.34. geometries_to_array

Împarte o geometrie într-o matrice cu geometrii mai simple.

Sintaxă

geometries_to_array(geometry)

Argumente

  • geometrie - geometria de intrare

Exemple

  • geometries_to_array(geom_from_wkt('GeometryCollection (Poligon ((5 8, 4 1, 3 2, 5 8)),LineString (3 2, 4 2))')) → o matrice de geometrii poligonale și liniare

  • geom_to_wkt(geometries_to_array(geom_from_wkt('GeometryCollection (Polygon ((5 8, 4 1, 3 2, 5 8)),LineString (3 2, 4 2))'))[0]) → «Polygon ((5 8, 4 1, 3 2, 5 8))»

  • geometries_to_array(geom_from_wkt('MULTIPOLYGON(((5 5,0 0,0 10,5 5)),((5 5,10 10,10 0,5 5))')) → o matrice cu două geometrii poligonale

13.2.2.35. regexp_matches

Returnează o matrice având toate șirurile capturate de grupuri, în ordinea în care grupurile însele apar în expresia regulată furnizată față de un șir.

Sintaxă

regexp_matches(string, regex, [empty_value=»»])

[] marks optional arguments

Argumente

  • șir - șirul din care expresia regulată va captura grupurile

  • regex - expresia regulată folosită pentru a captura grupuri

  • empty_value - the optional string to use as replacement for empty (zero length) matches

Exemple

  • regexp_matches('QGIS=>rocks','(.*)=>(.*)') → [ «QGIS», «rocks» ]

  • regexp_matches('key=>','(.*)=>(.*)','empty value') → [ «key», «empty value» ]

13.2.2.36. string_to_array

Împarte șirul într-o matrice, folosind delimitatorul furnizat și șirul opțional pentru valorile goale.

Sintaxă

string_to_array(string, [delimiter=»,»], [empty_value=»»])

[] marks optional arguments

Argumente

  • string - șirul de intrare

  • delimitator - delimitatorul folosit pentru a diviza șirul de intrare

  • empty_value - the optional string to use as replacement for empty (zero length) matches

Exemple

  • string_to_array('1,2,3',',') → [ «1», «2», «3» ]

  • string_to_array('1,,3',',','0') → [ «1», «0», «3» ]

13.2.3. Funcțiile Culorilor

Acest grup conține funcții pentru manipularea culorilor.

13.2.3.1. color_cmyk

Returnează o reprezentare de tip șir a unei culori, în funcție de componentele ei cyan, magenta, galben și negru

Sintaxă

color_cmyk(cyan, magenta, yellow, black)

Argumente

  • cyan - componenta cyan a culorii, ca valoare procentuală întreagă, de la 0 la 100

  • magenta - componenta magenta a culorii, ca valoare procentuală întreagă, de la 0 la 100

  • galben - componenta galbenă a culorii, ca valoare întreagă procentuală, de la 0 la 100

  • negru - componenta neagră a culorii, ca valoare întreagă procentuală, de la 0 la 100

Exemple

  • color_cmyk(100,50,0,10) → «0,115,230»

13.2.3.2. color_cmyka

Returnează o reprezentare de tip șir a unei culori, în funcție de componentele ei cyan, magenta, galben, negru și alpha (transparență)

Sintaxă

color_cmyka(cyan, magenta, yellow, black, alpha)

Argumente

  • cyan - componenta cyan a culorii, ca valoare procentuală întreagă, de la 0 la 100

  • magenta - componenta magenta a culorii, ca valoare procentuală întreagă, de la 0 la 100

  • galben - componenta galbenă a culorii, ca valoare întreagă procentuală, de la 0 la 100

  • negru - componenta neagră a culorii, ca valoare întreagă procentuală, de la 0 la 100

  • alfa - componentă alfa, ca valoare întreagă de la 0 (transparență completă) la 255 (opacitate completă).

Exemple

  • color_cmyka(100,50,0,10,200) → «0,115,230,200»

13.2.3.3. color_grayscale_average

Aplică un filtru în tonuri de gri și returnează o reprezentare sub formă de șir dintr-o culoare furnizată.

Sintaxă

color_grayscale_average(color)

Argumente

  • culoare - culoarea sub formă de șir

Exemple

  • color_grayscale_average('255,100,50') → «135,135,135,255»

13.2.3.4. color_hsl

Returnează o reprezentare sub formă de șir a unei culori, pe baza atributelor sale de nuanță, saturație și luminozitate.

Sintaxă

color_hsl(hue, saturation, lightness)

Argumente

  • hue - nuanța culorii, ca valoare întreagă, de la 0 la 360

  • saturation - procentajul saturației culorii, ca valoare întreagă, de la 0 la 100

  • lightness - procentul de luminozitate al culorii, ca valoare întreagă, de la 0 la 100

Exemple

  • color_hsl(100,50,70) → «166,217,140»

13.2.3.5. color_hsla

Returnează o reprezentare de tip șir a culorii, pe baza atributelor nuanței, saturației, luminozității și alpha (transparență)

Sintaxă

color_hsla(hue, saturation, lightness, alpha)

Argumente

  • hue - nuanța culorii, ca valoare întreagă, de la 0 la 360

  • saturation - procentajul saturației culorii, ca valoare întreagă, de la 0 la 100

  • lightness - procentul de luminozitate al culorii, ca valoare întreagă, de la 0 la 100

  • alfa - componentă alfa, ca valoare întreagă de la 0 (transparență completă) la 255 (opacitate completă).

Exemple

  • color_hsla(100,50,70,200) → «166,217,140,200»

13.2.3.6. color_hsv

Returnează o reprezentare sub formă de șir a unei culori, pe baza atributelor sale de nuanță, saturație și valoare.

Sintaxă

color_hsv(hue, saturation, value)

Argumente

  • hue - nuanța culorii, ca valoare întreagă, de la 0 la 360

  • saturation - procentajul saturației culorii, ca valoare întreagă, de la 0 la 100

  • value - valoare procentuală a culorii, ca număr întreg, de la 0 la 100

Exemple

  • color_hsv(40,100,100) → «255,170,0»

13.2.3.7. color_hsva

Returnează o reprezentare de tip șir a unei culori, bazată pe atributele nuanța, saturația, valoarea și alfa (transparență).

Sintaxă

color_hsva(hue, saturation, value, alpha)

Argumente

  • hue - nuanța culorii, ca valoare întreagă, de la 0 la 360

  • saturation - procentajul saturației culorii, ca valoare întreagă, de la 0 la 100

  • value - valoare procentuală a culorii, ca număr întreg, de la 0 la 100

  • alpha - componenta alfa, ca valoare întreagă de la 0 (transparență completă) la 255 (opacitate completă).

Exemple

  • color_hsva(40,100,100,200) → «255,170,0,200»

13.2.3.8. color_mix_rgb

Returnează un șir reprezentând o culoare dată de amestecul valorilor roșu, verde, albastru și alfa furnizate pentru două culori și în baza unei rații date.

Sintaxă

color_mix_rgb(color1, color2, ratio)

Argumente

  • color1 - culoarea 1 sub formă de șir

  • color2 - culoarea 2 sub formă de șir

  • ratio - rezultatul raportului dintre două valori

Exemple

  • color_mix_rgb('0,0,0','255,255,255',0.5) → «127,127,127,255»

13.2.3.9. color_part

Returnează o anumită componentă din șirul unei culori; de ex.: componenta roșie sau componenta alfa.

Sintaxă

color_part(color, component)

Argumente

  • culoare - culoarea sub formă de șir

  • component - un șir corespunzător componentei de culoare de returnat. Opțiunile valide sunt:

    • red: codul RGB al componentei roșii (0-255)

    • green: codul RGB al componentei verzi (0-255)

    • blue: codul RGB al componentei albastre (0-255)

    • alpha: valoarea alfa (transparența) (0-255)

    • hue: codul HSV al nuanței (0-360)

    • saturation: codul HSV al saturației (0-100)

    • value: codul HSV al valorii (0-100)

    • hsl_hue: codul HSL al nuanței (0-360)

    • hsl_saturation: codul HSL al saturației (0-100)

    • lightness: codul HSL al luminozității (0-100)

    • cyan: codul CMYK al componentei cyan (0-100)

    • magenta: codul CMYK al componentei magenta (0-100)

    • yellow: codul CMYK al componentei galbene (0-100)

    • black: codul CMYK al componentei negre (0-100)

Exemple

  • color_part('200,10,30','green') → 10

13.2.3.10. color_rgb

Returnează o reprezentare de tip șir a unei culori, în funcție de componentele sale roșie, verde și albastră.

Sintaxă

color_rgb(red, green, blue)

Argumente

  • red - componenta roșie, ca valoare întreagă de la 0 la 255

  • green - componenta verde, ca valoare întreagă de la 0 la 255

  • blue - componenta albastră, ca valoare întreagă de la 0 la 255

Exemple

  • color_rgb(255,127,0) → «255,127,0»

13.2.3.11. color_rgba

Returnează o reprezentare de tip șir a unei culori, în funcție de componentele sale roșie, verde, albastră și alfa (transparență).

Sintaxă

color_rgba(red, green, blue, alpha)

Argumente

  • red - componenta roșie, ca valoare întreagă de la 0 la 255

  • green - componenta verde, ca valoare întreagă de la 0 la 255

  • blue - componenta albastră, ca valoare întreagă de la 0 la 255

  • alfa - componentă alfa, ca valoare întreagă de la 0 (transparență completă) la 255 (opacitate completă).

Exemple

  • color_rgba(255,127,0,200) → «255,127,0,200»

13.2.3.12. create_ramp

Returnează o rampă gradientală pornind de la o hartă cu șiruri de culori și pași.

Sintaxă

create_ramp(map, [discrete=false])

[] marks optional arguments

Argumente

  • map - o hartă cu șiruri de culori și pași

  • discrete - setați acest parametru la true pentru a crea o rampă de culori discretă

Exemple

  • ramp_color(create_ramp(map(0,'0,0,0',1,'255,0,0')),1) → «255,0,0,255»

13.2.3.13. darker

Returnează o culoare, de tip șir, mai închisă (sau mai deschisă)

Sintaxă

darker(color, factor)

Argumente

  • culoare - culoarea sub formă de șir

  • factor - un număr întreg corespunzător factorului de întunecare:

    • dacă factorul este mai mare de 100, această funcție returnează o culoare mai închisă (de ex.: setarea factorului la 200 returnează o culoare care are o jumătate din luminozitate);

    • dacă factorul este mai mic de 100, culoarea returnată este mai deschisă; totuși, se recomandă utilizarea funcției lighter() în acest scop;

    • dacă factorul este 0 sau negativ, valoarea returnată este nespecificată.

Exemple

  • darker('200,10,30', 200) → «100,5,15,255»

Mai multe detalii: lighter

13.2.3.14. lighter

Returnează o culoare, de tip șir, mai deschisă (sau mai închisă)

Sintaxă

lighter(color, factor)

Argumente

  • culoare - culoarea sub formă de șir

  • factor - un număr întreg corespunzător factorului de iluminare:

    • dacă factorul este mai mare de 100, această funcție returnează o culoare mai deschisă (de ex.: setarea factorului la 150 returnează o culoare cu 50% mai strălucitoare);

    • dacă factorul este mai mic de 100, culoarea returnată este mai închisă; totuși, se recomandă utilizarea funcției darker() în acest scop;

    • dacă factorul este 0 sau negativ, valoarea returnată este nespecificată.

Exemple

  • lighter('200,10,30', 200) → «255,158,168,255»

Mai multe detalii: darker

13.2.3.15. project_color

Returnează o culoare din schema de culori a proiectului.

Sintaxă

project_color(name)

Argumente

  • nume - numele unei culori

Exemple

  • project_color('Logo color') → «20,140,50»

Mai multe detalii: setarea culorilor proiectului

13.2.3.16. ramp_color

Returnează un șir reprezentând o culoare dintr-o rampă de culoare.

Varianta salvată a rampei

Returnează un șir reprezentând o culoare dintr-o rampă salvată

Sintaxă

ramp_color(ramp_name, value)

Argumente

  • ramp_name - numele rampei de culoare, sub formă de șir, de ex.: „Spectral”

  • value - poziția de pe rampă, de unde se va selecta culoarea, ca număr real între 0 și 1

Exemple

  • ramp_color('Spectral',0.3) → «253,190,115,255»

Notă

Rampele de culoare disponibile variază în diversele versiuni de QGIS. Este posibil ca această funcție să nu dea rezultatele așteptate, dacă deschideți proiectul în alte versiuni de QGIS.

Variantă de rampă creată folosind expresii

Returnează un șir care reprezintă o culoare dintr-o rampă creată printr-o expresie

Sintaxă

ramp_color(ramp, value)

Argumente

  • ramp - rampa de culoare

  • value - poziția de pe rampă, de unde se va selecta culoarea, ca număr real între 0 și 1

Exemple

  • ramp_color(create_ramp(map(0,'0,0,0',1,'255,0,0')),1) → «255,0,0,255»

Mai multe detalii: Setting a Color Ramp, The color ramp drop-down shortcut

13.2.3.17. set_color_part

Setează o componentă de culoare specifică pentru șirul unei culori, de ex.: componenta roșie sau componenta alfa.

Sintaxă

set_color_part(color, component, value)

Argumente

  • culoare - culoarea sub formă de șir

  • component - un șir corespunzător componentei culorii de setat. Opțiunile valide sunt:

    • red: codul RGB al componentei roșii (0-255)

    • green: codul RGB al componentei verzi (0-255)

    • blue: codul RGB al componentei albastre (0-255)

    • alpha: valoarea alfa (transparența) (0-255)

    • hue: codul HSV al nuanței (0-360)

    • saturation: codul HSV al saturației (0-100)

    • value: codul HSV al valorii (0-100)

    • hsl_hue: codul HSL al nuanței (0-360)

    • hsl_saturation: codul HSL al saturației (0-100)

    • lightness: codul HSL al luminozității (0-100)

    • cyan: codul CMYK al componentei cyan (0-100)

    • magenta: codul CMYK al componentei magenta (0-100)

    • yellow: codul CMYK al componentei galbene (0-100)

    • black: codul CMYK al componentei negre (0-100)

  • value - noua valoare pentru componenta de culoare, respectând intervalele enumerate mai sus

Exemple

  • set_color_part('200,10,30','green',50) → «200,50,30,255»

13.2.4. Funcții Condiționale

Acest grup conține funcții care gestionează verificările condiționale din expresii.

13.2.4.1. CASE

CASE se folosește pentru a evalua o serie de condiții și pentru a returna un rezultat pentru prima condiție îndeplinită. Condițiile sunt evaluate secvențial, iar dacă o condiție este adevărată, evaluarea se oprește iar rezultatul corespunzător este returnat. Dacă niciuna dintre condiții nu este adevărată, se returnează valoarea din clauza ELSE. În plus, dacă nu este setată nicio clauză ELSE și nici una dintre condiții nu este îndeplinită, se returnează valoarea NULL.

CASE

WHEN condition THEN result

[ …n ]

[ ELSE result ]

END

[ ] marchează componentele opționale

Argumente

  • WHEN condition - Expresia condiției de evaluat

  • THEN result - Dacă condiția este evaluată la True, atunci este evaluat și returnat rezultatul.

  • ELSE result - Dacă niciuna dintre condițiile de mai sus nu este evaluată la True, atunci este evaluat și returnat rezultatul.

Exemple

  • CASE WHEN 'name' IS NULL THEN 'None' END → Returnează șirul «None» dacă câmpul „nume” este NULL

  • CASE WHEN $area > 10000 THEN 'Big property' WHEN $area > 5000 THEN 'Medium property' ELSE 'Small property' END → Returnează șirul «Big property» dacă aria este mai mare de 10000, «Medium property» dacă aria este între 5000 și 10000 și «Small property» în rest

13.2.4.2. coalesce

Returnează prima valoare non-NULL din lista de expresii.

Această funcție poate prelua orice număr de argumente.

Sintaxă

coalesce(expression1, expression2, …)

Argumente

  • expresie - orice expresie sau valoare validă, indiferent de tip.

Exemple

  • coalesce(NULL, 2) → 2

  • coalesce(NULL, 2, 3) → 2

  • coalesce(7, NULL, 3*2) → 7

  • coalesce('fieldA', 'fallbackField', 'ERROR') → valoarea câmpului A dacă nu este NULL, în caz contrar valoarea lui «fallbackField» sau șirul «ERROR» dacă ambele sunt NULL

13.2.4.3. if

Testează o condiție și returnează un rezultat diferit, în funcție de verificarea condiționată.

Sintaxă

if(condition, result_when_true, result_when_false)

Argumente

  • condition - condiția care ar trebui verificată

  • result_when_true - rezultatul care va fi returnat atunci când condiția este adevărată sau o altă valoare care nu se poate converti în fals.

  • result_when_false - rezultatul care va fi returnat atunci când condiția este falsă sau o altă valoare care se transformă în fals, cum ar fi 0 sau «». NULL se va converti, de asemenea, în fals.

Exemple

  • if( 1+1=2, 'Yes', 'No' ) → «Yes»

  • if( 1+1=3, 'Yes', 'No' ) → «No»

  • if( 5 > 3, 1, 0) → 1

  • if( '', 'It is true (not empty)', 'It is false (empty)' ) → «It is false (empty)»

  • if( ' ', 'It is true (not empty)', 'It is false (empty)' ) → «It is true (not empty)»

  • if( 0, 'One', 'Zero' ) → «Zero»

  • if( 10, 'One', 'Zero' ) → «One»

13.2.4.4. nullif

Returnează o valoare NULL dacă valoarea1 este egală cu valoarea2; în caz contrar, returnează valoarea1. Se poate folosi pentru a înlocui condiționat valorile cu NULL.

Sintaxă

nullif(value1, value2)

Argumente

  • value1 - Valoarea care ar trebui fie folosită, fie înlocuită cu NULL.

  • value2 - Valoarea de control care va declanșa substituirea cu NULL.

Exemple

  • nullif('(none)', '(none)') → NULL

  • nullif('text', '(none)') → «text»

  • nullif("name", '') → NULL, dacă numele este un șir vid (sau deja NULL), iar numele în restul cazurilor.

13.2.4.5. regexp_match

Return the first matching position matching a regular expression within an unicode string, or 0 if the substring is not found.

Sintaxă

regexp_match(input_string, regex)

Argumente

  • input_string - the string to test against the regular expression

  • regex - The regular expression to test against. Backslash characters must be double escaped (e.g., „\\s” to match a white space character or „\\b” to match a word boundary).

Exemple

  • regexp_match('QGIS ROCKS','\\sROCKS') → 5

  • regexp_match('Budač','udač\\b') → 2

13.2.4.6. try

Tries an expression and returns its value if error-free. If the expression returns an error, an alternative value will be returned when provided otherwise the function will return NULL.

Sintaxă

try(expression, [alternative])

[] marks optional arguments

Argumente

  • expression - the expression which should be run

  • alternative - the result which will be returned if the expression returns an error.

Exemple

  • try( to_int( '1' ), 0 ) → 1

  • try( to_int( 'a' ), 0 ) → 0

  • try( to_date( 'invalid_date' ) ) → NULL

13.2.5. Conversions Functions

This group contains functions to convert one data type to another (e.g., string from/to integer, binary from/to string, string to date, …).

13.2.5.1. from_base64

Decodes a string in the Base64 encoding into a binary value.

Sintaxă

from_base64(string)

Argumente

  • string - the string to decode

Exemple

  • from_base64('UUdJUw==') → «QGIS»

13.2.5.2. hash

Creates a hash from a string with a given method. One byte (8 bits) is represented with two hex «»digits»», so «md4» (16 bytes) produces a 16 * 2 = 32 character long hex string and «keccak_512» (64 bytes) produces a 64 * 2 = 128 character long hex string.

Sintaxă

hash(string, method)

Argumente

  • string - the string to hash

  • method - Metoda de codificare dintre «md4», «md5», «sha1», «sha224», «sha384», «sha512», «sha3_224», «sha3_256», «sha3_384», «sha3_512», «keccak_224», «keccak_256», «keccak_384», «keccak_512»

Exemple

  • hash('QGIS', 'md4') → «c0fc71c241cdebb6e888cbac0e2b68eb»

  • hash('QGIS', 'md5') → «57470aaa9e22adaefac7f5f342f1c6da»

  • hash('QGIS', 'sha1') → «f87cfb2b74cdd5867db913237024e7001e62b114»

  • hash('QGIS', 'sha224') → «4093a619ada631c770f44bc643ead18fb393b93d6a6af1861fcfece0»

  • hash('QGIS', 'sha256') → «eb045cba7a797aaa06ac58830846e40c8e8c780bc0676d3393605fae50c05309»

  • hash('QGIS', 'sha384') → «91c1de038cc3d09fdd512e99f9dd9922efadc39ed21d3922e69a4305cc25506033aee388e554b78714c8734f9cd7e610»

  • hash('QGIS', 'sha512') → «c2c092f2ab743bf8edbeb6d028a745f30fc720408465ed369421f0a4e20fa5e27f0c90ad72d3f1d836eaa5d25cd39897d4cf77e19984668ef58da6e3159f18ac»

  • hash('QGIS', 'sha3_224') → «467f49a5039e7280d5d42fd433e80d203439e338eaabd701f0d6c17d»

  • hash('QGIS', 'sha3_256') → «540f7354b6b8a6e735f2845250f15f4f3ba4f666c55574d9e9354575de0e980f»

  • hash('QGIS', 'sha3_384') → «96052da1e77679e9a65f60d7ead961b287977823144786386eb43647b0901fd8516fa6f1b9d243fb3f28775e6dde6107»

  • hash('QGIS', 'sha3_512') → «900d079dc69761da113980253aa8ac0414a8bd6d09879a916228f8743707c4758051c98445d6b8945ec854ff90655005e02aceb0a2ffc6a0ebf818745d665349»

  • hash('QGIS', 'keccak_224') → «5b0ce6acef8b0a121d4ac4f3eaa8503c799ad4e26a3392d1fb201478»

  • hash('QGIS', 'keccak_256') → «991c520aa6815392de24087f61b2ae0fd56abbfeee4a8ca019c1011d327c577e»

  • hash('QGIS', 'keccak_384') → «c57a3aed9d856fa04e5eeee9b62b6e027cca81ba574116d3cc1f0d48a1ef9e5886ff463ea8d0fac772ee473bf92f810d»

13.2.5.3. md5

Creează o codificare md5 dintr-un șir.

Sintaxă

md5(string)

Argumente

  • string - the string to hash

Exemple

  • md5('QGIS') → «57470aaa9e22adaefac7f5f342f1c6da»

13.2.5.4. sha256

Creează o codificare sha256 dintr-un șir.

Sintaxă

sha256(string)

Argumente

  • string - the string to hash

Exemple

  • sha256('QGIS') → «eb045cba7a797aaa06ac58830846e40c8e8c780bc0676d3393605fae50c05309»

13.2.5.5. to_base64

Codifică o valoare binară într-un șir, folosind Base64.

Sintaxă

to_base64(value)

Argumente

  • value - valoarea binară de codificat

Exemple

  • to_base64('QGIS') → «UUdJUw==»

13.2.5.6. to_date

Converts a string into a date object. An optional format string can be provided to parse the string; see QDate::fromString or the documentation of the format_date function for additional documentation on the format. By default the current QGIS user locale is used.

Sintaxă

to_date(string, [format], [language])

[] marks optional arguments

Argumente

  • string - string representing a date value

  • format - format used to convert the string into a date

  • language - language (lowercase, two- or three-letter, ISO 639 language code) used to convert the string into a date. By default the current QGIS user locale is used.

Exemple

  • to_date('2012-05-04') → 2012-05-04

  • to_date('June 29, 2019','MMMM d, yyyy') → 2019-06-29, if the current locale uses the name «June» for the sixth month, otherwise an error occurs

  • to_date('29 juin, 2019','d MMMM, yyyy','fr') → 2019-06-29

13.2.5.7. to_datetime

Converts a string into a datetime object. An optional format string can be provided to parse the string; see QDate::fromString, QTime::fromString or the documentation of the format_date function for additional documentation on the format. By default the current QGIS user locale is used.

Sintaxă

to_datetime(string, [format], [language])

[] marks optional arguments

Argumente

  • string - string representing a datetime value

  • format - format used to convert the string into a datetime

  • language - language (lowercase, two- or three-letter, ISO 639 language code) used to convert the string into a datetime. By default the current QGIS user locale is used.

Exemple

  • to_datetime('2012-05-04 12:50:00') → 2012-05-04T12:50:00

  • to_datetime('June 29, 2019 @ 12:34','MMMM d, yyyy @ HH:mm') → 2019-06-29T12:34, if the current locale uses the name «June» for the sixth month, otherwise an error occurs

  • to_datetime('29 juin, 2019 @ 12:34','d MMMM, yyyy @ HH:mm','fr') → 2019-06-29T12:34

13.2.5.8. to_decimal

Converts a degree, minute, second coordinate to its decimal equivalent.

Sintaxă

to_decimal(value)

Argumente

  • value - A degree, minute, second string.

Exemple

  • to_decimal('6°21\'16.445') → 6.3545680555

13.2.5.9. to_dm

Converts a coordinate to degree, minute.

Sintaxă

to_dm(coordinate, axis, precision, [formatting=])

[] marks optional arguments

Argumente

  • coordinate - A latitude or longitude value.

  • axis - The axis of the coordinate. Either «x» or «y».

  • precision - Numărul de zecimale.

  • formatting - Designates the formatting type. Acceptable values are NULL (default), «aligned» or «suffix».

Exemple

  • to_dm(6.1545681, 'x', 3) → 6°9.274′

  • to_dm(6.1545681, 'y', 4, 'aligned') → 6°09.2741′N

  • to_dm(6.1545681, 'y', 4, 'suffix') → 6°9.2741′N

13.2.5.10. to_dms

Converts a coordinate to degree, minute, second.

Sintaxă

to_dms(coordinate, axis, precision, [formatting=])

[] marks optional arguments

Argumente

  • coordinate - A latitude or longitude value.

  • axis - The axis of the coordinate. Either «x» or «y».

  • precision - Numărul de zecimale.

  • formatting - Designates the formatting type. Acceptable values are NULL (default), «aligned» or «suffix».

Exemple

  • to_dms(6.1545681, 'x', 3) → 6°9′16.445″

  • to_dms(6.1545681, 'y', 4, 'aligned') → 6°09′16.4452″N

  • to_dms(6.1545681, 'y', 4, 'suffix') → 6°9′16.4452″N

13.2.5.11. to_int

Converts a string to integer number. Nothing is returned if a value cannot be converted to integer (e.g «123asd» is invalid).

Sintaxă

to_int(string)

Argumente

  • string - string to convert to integer number

Exemple

  • to_int('123') → 123

13.2.5.12. to_interval

Converts a string to an interval type. Can be used to take days, hours, month, etc of a date.

Sintaxă

to_interval(string)

Argumente

  • string - a string representing an interval. Allowable formats include {n} days {n} hours {n} months.

Exemple

  • to_interval('1 day 2 hours') → interval: 1.08333 days

  • to_interval( '0.5 hours' ) → interval: 30 minutes

  • to_datetime('2012-05-05 12:00:00') - to_interval('1 day 2 hours') → 2012-05-04T10:00:00

13.2.5.13. to_real

Converts a string to a real number. Nothing is returned if a value cannot be converted to real (e.g «123.56asd» is invalid). Numbers are rounded after saving changes if the precision is smaller than the result of the conversion.

Sintaxă

to_real(string)

Argumente

  • string - string to convert to real number

Exemple

  • to_real('123.45') → 123.45

13.2.5.14. to_string

Convertește un număr într-un șir.

Sintaxă

to_string(number)

Argumente

  • number - Număr întreg sau valoare reală. Numărul de convertit în șir.

Exemple

  • to_string(123) → «123»

13.2.5.15. to_time

Converts a string into a time object. An optional format string can be provided to parse the string; see QTime::fromString for additional documentation on the format.

Sintaxă

to_time(string, [format], [language])

[] marks optional arguments

Argumente

  • string - string representing a time value

  • format - format used to convert the string into a time

  • language - language (lowercase, two- or three-letter, ISO 639 language code) used to convert the string into a time

Exemple

  • to_time('12:30:01') → 12:30:01

  • to_time('12:34','HH:mm') → 12:34:00

  • to_time('12:34','HH:mm','fr') → 12:34:00

13.2.6. Funcții Personalizate

This group contains functions created by the user. See Editorul de Funcții for more details.

13.2.7. Funcții pentru Dată și Oră

This group contains functions for handling date and time data. This group shares several functions with the Conversions Functions (to_date, to_time, to_datetime, to_interval) and Funcții pentru Șiruri (format_date) groups.

Notă

Storing date, datetime and intervals on fields

The ability to store date, time and datetime values directly on fields depends on the data source’s provider (e.g., Shapefile accepts date format, but not datetime or time format). The following are some suggestions to overcome this limitation:

  • date, datetime and time can be converted and stored in text type fields using the format_date() function.

  • Intervals can be stored in integer or decimal type fields after using one of the date extraction functions (e.g., day() to get the interval expressed in days)

13.2.7.1. age

Returns the difference between two dates or datetimes.

The difference is returned as an Interval and needs to be used with one of the following functions in order to extract useful information:

  • year

  • month

  • week

  • day

  • hour

  • minute

  • second

Sintaxă

age(datetime1, datetime2)

Argumente

  • datetime1 - un șir, dată sau datetime care reprezintă o dată ulterioară

  • datetime2 - un șir, dată sau datetime care reprezintă data anterioară

Exemple

  • day(age('2012-05-12','2012-05-02')) → 10

  • hour(age('2012-05-12','2012-05-02')) → 240

13.2.7.2. datetime_from_epoch

Returns a datetime whose date and time are the number of milliseconds, msecs, that have passed since 1970-01-01T00:00:00.000, Coordinated Universal Time (Qt.UTC), and converted to Qt.LocalTime.

Sintaxă

datetime_from_epoch(int)

Argumente

  • int - număr (milisecunde)

Exemple

  • datetime_from_epoch(1483225200000) → 2017-01-01T00:00:00

13.2.7.3. day

Extrage ziua dintr-o dată sau numărul de zile dintr-un interval.

Date variant

Extracts the day from a date or datetime.

Sintaxă

day(date)

Argumente

  • date - a date or datetime value

Exemple

  • day('2012-05-12') → 12

Interval variant

Calculates the length in days of an interval.

Sintaxă

day(interval)

Argumente

  • interval - interval value to return number of days from

Exemple

  • day(to_interval('3 days')) → 3

  • day(to_interval('3 weeks 2 days')) → 23

  • day(age('2012-01-01','2010-01-01')) → 730

13.2.7.4. day_of_week

Returns the day of the week for a specified date or datetime. The returned value ranges from 0 to 6, where 0 corresponds to a Sunday and 6 to a Saturday.

Sintaxă

day_of_week(date)

Argumente

  • date - date or datetime value

Exemple

  • day_of_week(to_date('2015-09-21')) → 1

13.2.7.5. epoch

Returns the interval in milliseconds between the unix epoch and a given date value.

Sintaxă

epoch(date)

Argumente

  • date - a date or datetime value

Exemple

  • epoch(to_date('2017-01-01')) → 1483203600000

13.2.7.6. format_date

Formats a date type or string into a custom string format. Uses Qt date/time format strings. See QDateTime::toString.

Sintaxă

format_date(datetime, format, [language])

[] marks optional arguments

Argumente

  • datetime - date, time or datetime value

  • format - String template used to format the string.

    Expression

    Rezultat

    d

    ziua, un număr fără zero la început (de la 1 la 31)

    dd

    ziua, un număr cu zero la început (de la 01 la 31)

    ddd

    the abbreviated localized day name (e.g. «Mon» to «Sun»)

    dddd

    the long localized day name (e.g. «Monday» to «Sunday»)

    M

    the month as number without a leading zero (1-12)

    MM

    the month as number with a leading zero (01-12)

    MMM

    the abbreviated localized month name (e.g. «Jan» to «Dec»)

    MMMM

    the long localized month name (e.g. «January» to «December»)

    yy

    the year as two digit number (00-99)

    yyyy

    the year as four digit number

    These expressions may be used for the time part of the format string:

    Expression

    Rezultat

    h

    the hour without a leading zero (0 to 23 or 1 to 12 if AM/PM display)

    hh

    the hour with a leading zero (00 to 23 or 01 to 12 if AM/PM display)

    H

    the hour without a leading zero (0 to 23, even with AM/PM display)

    HH

    the hour with a leading zero (00 to 23, even with AM/PM display)

    m

    minutul, fără zero la început (de la 0 la 59)

    mm

    minutul, cu zero la început (de la 00 la 59)

    s

    secunda, fără zero la început (de la 0 la 59)

    ss

    secunda, cu un zero la început (de la 00 la 59)

    z

    the milliseconds without trailing zeroes (0 to 999)

    zzz

    the milliseconds with trailing zeroes (000 to 999)

    AP or A

    interpret as an AM/PM time. AP must be either «AM» or «PM».

    ap or a

    Interpret as an AM/PM time. ap must be either «am» or «pm».

  • language - language (lowercase, two- or three-letter, ISO 639 language code) used to format the date into a custom string. By default the current QGIS user locale is used.

Exemple

  • format_date('2012-05-15','dd.MM.yyyy') → «15.05.2012»

  • format_date('2012-05-15','d MMMM yyyy','fr') → «15 mai 2012»

  • format_date('2012-05-15','dddd') → «Tuesday», if the current locale is an English variant

  • format_date('2012-05-15 13:54:20','dd.MM.yy') → «15.05.12»

  • format_date('13:54:20','hh:mm AP') → «01:54 PM»

13.2.7.7. hour

Extracts the hour part from a datetime or time, or the number of hours from an interval.

Time variant

Extracts the hour part from a time or datetime.

Sintaxă

hour(datetime)

Argumente

  • datetime - a time or datetime value

Exemple

  • hour( to_datetime('2012-07-22 13:24:57') ) → 13

Interval variant

Calculates the length in hours of an interval.

Sintaxă

hour(interval)

Argumente

  • interval - interval value to return number of hours from

Exemple

  • hour(to_interval('3 hours')) → 3

  • hour(age('2012-07-22T13:00:00','2012-07-22T10:00:00')) → 3

  • hour(age('2012-01-01','2010-01-01')) → 17520

13.2.7.8. make_date

Creates a date value from year, month and day numbers.

Sintaxă

make_date(year, month, day)

Argumente

  • year - Year number. Years 1 to 99 are interpreted as is. Year 0 is invalid.

  • month - Month number, where 1=January

  • day - Day number, beginning with 1 for the first day in the month

Exemple

  • make_date(2020,5,4) → date value 2020-05-04

13.2.7.9. make_datetime

Creates a datetime value from year, month, day, hour, minute and second numbers.

Sintaxă

make_datetime(year, month, day, hour, minute, second)

Argumente

  • year - Year number. Years 1 to 99 are interpreted as is. Year 0 is invalid.

  • month - Month number, where 1=January

  • day - Day number, beginning with 1 for the first day in the month

  • hour - Ora

  • minute - Minute

  • second - Secunde (valorile facționale includ milisecunde)

Exemple

  • make_datetime(2020,5,4,13,45,30.5) → datetime value 2020-05-04 13:45:30.500

13.2.7.10. make_interval

Creează o valoare de tip interval din valorile an, lună, săptămâni, zile, ore, minute și secunde.

Sintaxă

make_interval([years=0], [months=0], [weeks=0], [days=0], [hours=0], [minutes=0], [seconds=0])

[] marks optional arguments

Argumente

  • years - Numărul de ani (presupunând o lungime a anului de 365,25 zile).

  • months - Number of months (assumes a 30 day month length)

  • weeks - Numărul de săptămâni

  • days - Numărul de zile

  • hours - Numărul de ore

  • minutes - Numărul de minute

  • seconds - Numărul de secunde

Exemple

  • make_interval(hours:=3) → interval: 3 ore

  • make_interval(days:=2, hours:=3) → interval: 2.125 zile

  • make_interval(minutes:=0.5, seconds:=5) → interval: 35 secounde

13.2.7.11. make_time

Creates a time value from hour, minute and second numbers.

Sintaxă

make_time(hour, minute, second)

Argumente

  • hour - Ora

  • minute - Minute

  • second - Secunde (valorile facționale includ milisecunde)

Exemple

  • make_time(13,45,30.5) → time value 13:45:30.500

13.2.7.12. minute

Extracts the minutes part from a datetime or time, or the number of minutes from an interval.

Time variant

Extracts the minutes part from a time or datetime.

Sintaxă

minute(datetime)

Argumente

  • datetime - a time or datetime value

Exemple

  • minute( to_datetime('2012-07-22 13:24:57') ) → 24

Interval variant

Calculates the length in minutes of an interval.

Sintaxă

minute(interval)

Argumente

  • interval - interval value to return number of minutes from

Exemple

  • minute(to_interval('3 minutes')) → 3

  • minute(age('2012-07-22T00:20:00','2012-07-22T00:00:00')) → 20

  • minute(age('2012-01-01','2010-01-01')) → 1051200

13.2.7.13. month

Extracts the month part from a date, or the number of months from an interval.

Date variant

Extracts the month part from a date or datetime.

Sintaxă

month(date)

Argumente

  • date - a date or datetime value

Exemple

  • month('2012-05-12') → 05

Interval variant

Calculates the length in months of an interval.

Sintaxă

month(interval)

Argumente

  • interval - interval value to return number of months from

Exemple

  • month(to_interval('3 months')) → 3

  • month(age('2012-01-01','2010-01-01')) → 4.03333

13.2.7.14. now

Returns the current date and time. The function is static and will return consistent results while evaluating. The time returned is the time when the expression is prepared.

Sintaxă

now()

Exemple

  • now() → 2012-07-22T13:24:57

13.2.7.15. second

Extracts the seconds part from a datetime or time, or the number of seconds from an interval.

Time variant

Extracts the seconds part from a time or datetime.

Sintaxă

second(datetime)

Argumente

  • datetime - a time or datetime value

Exemple

  • second( to_datetime('2012-07-22 13:24:57') ) → 57

Interval variant

Calculates the length in seconds of an interval.

Sintaxă

second(interval)

Argumente

  • interval - interval value to return number of seconds from

Exemple

  • second(to_interval('3 minutes')) → 180

  • second(age('2012-07-22T00:20:00','2012-07-22T00:00:00')) → 1200

  • second(age('2012-01-01','2010-01-01')) → 63072000

13.2.7.16. to_date

Converts a string into a date object. An optional format string can be provided to parse the string; see QDate::fromString or the documentation of the format_date function for additional documentation on the format. By default the current QGIS user locale is used.

Sintaxă

to_date(string, [format], [language])

[] marks optional arguments

Argumente

  • string - string representing a date value

  • format - format used to convert the string into a date

  • language - language (lowercase, two- or three-letter, ISO 639 language code) used to convert the string into a date. By default the current QGIS user locale is used.

Exemple

  • to_date('2012-05-04') → 2012-05-04

  • to_date('June 29, 2019','MMMM d, yyyy') → 2019-06-29, if the current locale uses the name «June» for the sixth month, otherwise an error occurs

  • to_date('29 juin, 2019','d MMMM, yyyy','fr') → 2019-06-29

13.2.7.17. to_datetime

Converts a string into a datetime object. An optional format string can be provided to parse the string; see QDate::fromString, QTime::fromString or the documentation of the format_date function for additional documentation on the format. By default the current QGIS user locale is used.

Sintaxă

to_datetime(string, [format], [language])

[] marks optional arguments

Argumente

  • string - string representing a datetime value

  • format - format used to convert the string into a datetime

  • language - language (lowercase, two- or three-letter, ISO 639 language code) used to convert the string into a datetime. By default the current QGIS user locale is used.

Exemple

  • to_datetime('2012-05-04 12:50:00') → 2012-05-04T12:50:00

  • to_datetime('June 29, 2019 @ 12:34','MMMM d, yyyy @ HH:mm') → 2019-06-29T12:34, if the current locale uses the name «June» for the sixth month, otherwise an error occurs

  • to_datetime('29 juin, 2019 @ 12:34','d MMMM, yyyy @ HH:mm','fr') → 2019-06-29T12:34

13.2.7.18. to_interval

Converts a string to an interval type. Can be used to take days, hours, month, etc of a date.

Sintaxă

to_interval(string)

Argumente

  • string - a string representing an interval. Allowable formats include {n} days {n} hours {n} months.

Exemple

  • to_interval('1 day 2 hours') → interval: 1.08333 days

  • to_interval( '0.5 hours' ) → interval: 30 minutes

  • to_datetime('2012-05-05 12:00:00') - to_interval('1 day 2 hours') → 2012-05-04T10:00:00

13.2.7.19. to_time

Converts a string into a time object. An optional format string can be provided to parse the string; see QTime::fromString for additional documentation on the format.

Sintaxă

to_time(string, [format], [language])

[] marks optional arguments

Argumente

  • string - string representing a time value

  • format - format used to convert the string into a time

  • language - language (lowercase, two- or three-letter, ISO 639 language code) used to convert the string into a time

Exemple

  • to_time('12:30:01') → 12:30:01

  • to_time('12:34','HH:mm') → 12:34:00

  • to_time('12:34','HH:mm','fr') → 12:34:00

13.2.7.20. week

Extracts the week number from a date, or the number of weeks from an interval.

Date variant

Extracts the week number from a date or datetime.

Sintaxă

week(date)

Argumente

  • date - a date or datetime value

Exemple

  • week('2012-05-12') → 19

Interval variant

Calculates the length in weeks of an interval.

Sintaxă

week(interval)

Argumente

  • interval - interval value to return number of months from

Exemple

  • week(to_interval('3 weeks')) → 3

  • week(age('2012-01-01','2010-01-01')) → 104.285

13.2.7.21. year

Extracts the year part from a date, or the number of years from an interval.

Date variant

Extracts the year part from a date or datetime.

Sintaxă

year(date)

Argumente

  • date - a date or datetime value

Exemple

  • year('2012-05-12') → 2012

Interval variant

Calculates the length in years of an interval.

Sintaxă

year(interval)

Argumente

  • interval - interval value to return number of years from

Exemple

  • year(to_interval('3 years')) → 3

  • year(age('2012-01-01','2010-01-01')) → 1.9986

Câteva exemple:

Besides these functions, subtracting dates, datetimes or times using the - (minus) operator will return an interval.

Adding or subtracting an interval to dates, datetimes or times, using the + (plus) and - (minus) operators, will return a datetime.

  • Get the number of days until QGIS 3.0 release:

    to_date('2017-09-29') - to_date(now())
    -- Returns <interval: 203 days>
    
  • The same with time:

    to_datetime('2017-09-29 12:00:00') - now()
    -- Returns <interval: 202.49 days>
    
  • Get the datetime of 100 days from now:

    now() + to_interval('100 days')
    -- Returns <datetime: 2017-06-18 01:00:00>
    

13.2.8. Fields and Values

Contains a list of fields from the active layer, and special values. Fields list includes the ones stored in the dataset, virtual and auxiliary ones as well as from joins.

Double-click a field name to have it added to your expression. You can also type the field name (preferably inside double quotes) or its alias.

To retrieve fields values to use in an expression, select the appropriate field and, in the shown widget, choose between 10 Samples and All Unique. Requested values are then displayed and you can use the Search box at the top of the list to filter the result. Sample values can also be accessed via right-clicking on a field.

To add a value to the expression you are writing, double-click on it in the list. If the value is of a string type, it should be simple quoted, otherwise no quote is needed.

13.2.8.1. NULL

Echivalează cu o valoare NULL.

Sintaxă

NULL

Exemple

  • NULL → o valoare NULL

Notă

To test for NULL use an IS NULL or IS NOT NULL expression.

13.2.9. Files and Paths Functions

Acest grup conține funcții care manipulează numele fișierelor și căilor.

13.2.9.1. base_file_name

Returnează numele de bază al fișierului, fără directorul sau sufixul fișierului.

Sintaxă

base_file_name(path)

Argumente

  • path - o cale de fișier sau o valoare a unui strat de hartă. Dacă este specificată o valoare a unui strat de hartă, atunci va fi folosită sursa fișierului stratului.

Exemple

  • base_file_name('/home/qgis/data/country_boundaries.shp') → «country_boundaries»

13.2.9.2. exif

Preia valorile etichetelor exif dintr-un fișier imagine.

Sintaxă

exif(path, [tag])

[] marks optional arguments

Argumente

  • cale - O cale a unui fișier de tip imagine sau o valoare a unui strat de hartă. Dacă este specificată o valoare a unui strat de hartă, atunci se va folosi sursa fișierului stratului.

  • tag - Eticheta de returnat. Dacă se lasă necompletat, atunci se va returna o hartă cu toate valorile etichetelor exif.

Exemple

  • exif('/my/photo.jpg','Exif.Image.Orientation') → 0

13.2.9.3. file_exists

Returnează TRUE dacă există o cale de fișier.

Sintaxă

file_exists(path)

Argumente

  • path - o cale de fișier sau o valoare a unui strat de hartă. Dacă este specificată o valoare a unui strat de hartă, atunci va fi folosită sursa fișierului stratului.

Exemple

  • file_exists('/home/qgis/data/country_boundaries.shp') → TRUE

13.2.9.4. file_name

Returnează numele unui fișier (inclusiv extensia fișierului), excluzând directorul.

Sintaxă

file_name(path)

Argumente

  • path - o cale de fișier sau o valoare a unui strat de hartă. Dacă este specificată o valoare a unui strat de hartă, atunci va fi folosită sursa fișierului stratului.

Exemple

  • file_name('/home/qgis/data/country_boundaries.shp') → «country_boundaries.shp»

13.2.9.5. file_path

Returnează directorul, din compunerea unei căi de fișier. Nu se include și numele fișierului.

Sintaxă

file_path(path)

Argumente

  • path - o cale de fișier sau o valoare a unui strat de hartă. Dacă este specificată o valoare a unui strat de hartă, atunci va fi folosită sursa fișierului stratului.

Exemple

  • file_path('/home/qgis/data/country_boundaries.shp') → «/home/qgis/data»

13.2.9.6. file_size

Returnează dimensiunea (în octeți) a unui fișier.

Sintaxă

file_size(path)

Argumente

  • path - o cale de fișier sau o valoare a unui strat de hartă. Dacă este specificată o valoare a unui strat de hartă, atunci va fi folosită sursa fișierului stratului.

Exemple

  • file_size('/home/qgis/data/country_boundaries.geojson') → 5674

13.2.9.7. file_suffix

Returnează sufixul fișierului (extensia) dintr-o cale de fișier.

Sintaxă

file_suffix(path)

Argumente

  • path - o cale de fișier sau o valoare a unui strat de hartă. Dacă este specificată o valoare a unui strat de hartă, atunci va fi folosită sursa fișierului stratului.

Exemple

  • file_suffix('/home/qgis/data/country_boundaries.shp') → «shp»

13.2.9.8. is_directory

Returnează TRUE dacă o cale corespunde unui director.

Sintaxă

is_directory(path)

Argumente

  • path - o cale de fișier sau o valoare a unui strat de hartă. Dacă este specificată o valoare a unui strat de hartă, atunci va fi folosită sursa fișierului stratului.

Exemple

  • is_directory('/home/qgis/data/country_boundaries.shp') → FALSE

  • is_directory('/home/qgis/data/') → TRUE

13.2.9.9. is_file

Returns TRUE if a path corresponds to a file.

Sintaxă

is_file(path)

Argumente

  • path - o cale de fișier sau o valoare a unui strat de hartă. Dacă este specificată o valoare a unui strat de hartă, atunci va fi folosită sursa fișierului stratului.

Exemple

  • is_file('/home/qgis/data/country_boundaries.shp') → TRUE

  • is_file('/home/qgis/data/') → FALSE

13.2.10. Form Functions

This group contains functions that operate exclusively under the attribute form context. For example, in field’s widgets settings.

13.2.10.1. current_parent_value

Only usable in an embedded form context, this function returns the current, unsaved value of a field in the parent form currently being edited. This will differ from the parent feature’s actual attribute values for features which are currently being edited or have not yet been added to a parent layer. When used in a value-relation widget filter expression, this function should be wrapped into a «coalesce()» that can retrieve the actual parent feature from the layer when the form is not used in an embedded context.

Sintaxă

current_parent_value(field_name)

Argumente

  • field_name - a field name in the current parent form

Exemple

  • current_parent_value( 'FIELD_NAME' ) → The current value of a field «FIELD_NAME» in the parent form.

13.2.10.2. current_value

Returns the current, unsaved value of a field in the form or table row currently being edited. This will differ from the feature’s actual attribute values for features which are currently being edited or have not yet been added to a layer.

Sintaxă

current_value(field_name)

Argumente

  • field_name - a field name in the current form or table row

Exemple

  • current_value( 'FIELD_NAME' ) → The current value of field «FIELD_NAME».

13.2.11. Funcții pentru Potrivirea Fuzzy

Acest grup conține funcții pentru comparații fuzzy între valori.

13.2.11.1. hamming_distance

Returns the Hamming distance between two strings. This equates to the number of characters at corresponding positions within the input strings where the characters are different. The input strings must be the same length, and the comparison is case-sensitive.

Sintaxă

hamming_distance(string1, string2)

Argumente

  • string1 - a string

  • string2 - a string

Exemple

  • hamming_distance('abc','xec') → 2

  • hamming_distance('abc','ABc') → 2

  • hamming_distance(upper('abc'),upper('ABC')) → 0

  • hamming_distance('abc','abcd') → NULL

13.2.11.2. levenshtein

Returns the Levenshtein edit distance between two strings. This equates to the minimum number of character edits (insertions, deletions or substitutions) required to change one string to another.

The Levenshtein distance is a measure of the similarity between two strings. Smaller distances mean the strings are more similar, and larger distances indicate more different strings. The distance is case sensitive.

Sintaxă

levenshtein(string1, string2)

Argumente

  • string1 - a string

  • string2 - a string

Exemple

  • levenshtein('kittens','mitten') → 2

  • levenshtein('Kitten','kitten') → 1

  • levenshtein(upper('Kitten'),upper('kitten')) → 0

13.2.11.3. longest_common_substring

Returns the longest common substring between two strings. This substring is the longest string that is a substring of the two input strings. For example, the longest common substring of „ABABC” and „BABCA” is „BABC”. The substring is case sensitive.

Sintaxă

longest_common_substring(string1, string2)

Argumente

  • string1 - a string

  • string2 - a string

Exemple

  • longest_common_substring('ABABC','BABCA') → «BABC»

  • longest_common_substring('abcDeF','abcdef') → «abc»

  • longest_common_substring(upper('abcDeF'),upper('abcdex')) → «ABCDE»

13.2.11.4. soundex

Returns the Soundex representation of a string. Soundex is a phonetic matching algorithm, so strings with similar sounds should be represented by the same Soundex code.

Sintaxă

soundex(string)

Argumente

  • string - a string

Exemple

  • soundex('robert') → «R163»

  • soundex('rupert') → «R163»

  • soundex('rubin') → «R150»

13.2.12. Funcții Generale

This group contains general assorted functions.

13.2.12.1. env

Gets an environment variable and returns its content as a string. If the variable is not found, NULL will be returned. This is handy to inject system specific configuration like drive letters or path prefixes. Definition of environment variables depends on the operating system, please check with your system administrator or the operating system documentation how this can be set.

Sintaxă

env(name)

Argumente

  • name - The name of the environment variable which should be retrieved.

Exemple

  • env( 'LANG' ) → «en_US.UTF-8»

  • env( 'MY_OWN_PREFIX_VAR' ) → «Z:»

  • env( 'I_DO_NOT_EXIST' ) → NULL

13.2.12.2. eval

Evaluates an expression which is passed in a string. Useful to expand dynamic parameters passed as context variables or fields.

Sintaxă

eval(expression)

Argumente

  • expression - an expression string

Exemple

  • eval('\'nice\'') → «nice»

  • eval(@expression_var) → [whatever the result of evaluating @expression_var might be…]

13.2.12.3. eval_template

Evaluates a template which is passed in a string. Useful to expand dynamic parameters passed as context variables or fields.

Sintaxă

eval_template(template)

Argumente

  • template - a template string

Exemple

  • eval_template('QGIS [% upper(\'rocks\') %]') → QGIS ROCKS

13.2.12.4. is_layer_visible

Returns TRUE if a specified layer is visible.

Sintaxă

is_layer_visible(layer)

Argumente

  • layer - a string, representing either a layer name or layer ID

Exemple

  • is_layer_visible('baseraster') → TRUE

13.2.12.5. mime_type

Returns the mime type of the binary data.

Sintaxă

mime_type(bytes)

Argumente

  • bytes - the binary data

Exemple

  • mime_type('<html><body></body></html>') → text/html

  • mime_type(from_base64('R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAIAOw==')) → image/gif

13.2.12.6. var

Returns the value stored within a specified variable.

Sintaxă

var(name)

Argumente

  • name - a variable name

Exemple

  • var('qgis_version') → «2.12»

Mai multe detalii: Lista variabilelor implicite :ref:` <expression_variables>`

13.2.12.7. with_variable

This function sets a variable for any expression code that will be provided as 3rd argument. This is only useful for complicated expressions, where the same calculated value needs to be used in different places.

Sintaxă

with_variable(name, value, expression)

Argumente

  • name - the name of the variable to set

  • value - the value to set

  • expression - the expression for which the variable will be available

Exemple

  • with_variable('my_sum', 1 + 2 + 3, @my_sum * 2 + @my_sum * 5) → 42

13.2.13. Funcții Geometrice

This group contains functions that operate on geometry objects (e.g. buffer, transform, $area).

13.2.13.1. affine_transform

Returns the geometry after an affine transformation. Calculations are in the Spatial Reference System of this geometry. The operations are performed in a scale, rotation, translation order. If there is a Z or M offset but the coordinate is not present in the geometry, it will be added.

Sintaxă

affine_transform(geometry, delta_x, delta_y, rotation_z, scale_x, scale_y, [delta_z=0], [delta_m=0], [scale_z=1], [scale_m=1])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • delta_x - x-axis translation

  • delta_y - y-axis translation

  • rotation_z - rotation around z-axis in degrees counter-clockwise

  • scale_x - x-axis scale factor

  • scale_y - y-axis scale factor

  • delta_z - z-axis translation

  • delta_m - m-axis translation

  • scale_z - z-axis scale factor

  • scale_m - m-axis scale factor

Exemple

  • geom_to_wkt(affine_transform(geom_from_wkt('LINESTRING(1 1, 2 2)'), 2, 2, 0, 1, 1)) → «LineString (3 3, 4 4)»

  • geom_to_wkt(affine_transform(geom_from_wkt('POLYGON((0 0, 0 3, 2 2, 0 0))'), 0, 0, -90, 1, 2)) → «Polygon ((0 0, 6 0, 4 -2, 0 0))»

  • geom_to_wkt(affine_transform(geom_from_wkt('POINT(3 1)'), 0, 0, 0, 1, 1, 5, 0)) → «PointZ (3 1 5)»

../../../_images/affinetransform.png

Fig. 13.4 Vector point layer (green dots) before (left), and after (right) an affine transformation (translation).

13.2.13.2. angle_at_vertex

Returns the bisector angle (average angle) to the geometry for a specified vertex on a linestring geometry. Angles are in degrees clockwise from north.

Sintaxă

angle_at_vertex(geometry, vertex)

Argumente

  • geometry - a linestring geometry

  • vertex - vertex index, starting from 0; if the value is negative, the selected vertex index will be its total count minus the absolute value

Exemple

  • angle_at_vertex(geometry:=geom_from_wkt('LineString(0 0, 10 0, 10 10)'),vertex:=1) → 45.0

13.2.13.3. apply_dash_pattern

Applies a dash pattern to a geometry, returning a MultiLineString geometry which is the input geometry stroked along each line/ring with the specified pattern.

Sintaxă

apply_dash_pattern(geometry, pattern, [start_rule=no_rule], [end_rule=no_rule], [adjustment=both], [pattern_offset=0])

[] marks optional arguments

Argumente

  • geometry - a geometry (accepts (multi)linestrings or (multi)polygons).

  • pattern - dash pattern, as an array of numbers representing dash and gap lengths. Must contain an even number of elements.

  • start_rule - optional rule for constraining the start of the pattern. Valid values are «no_rule», «full_dash», «half_dash», «full_gap», «half_gap».

  • end_rule - optional rule for constraining the end of the pattern. Valid values are «no_rule», «full_dash», «half_dash», «full_gap», «half_gap».

  • adjustment - optional rule for specifying which part of patterns are adjusted to fit the desired pattern rules. Valid values are «both», «dash», «gap».

  • pattern_offset - Optional distance specifying a specific distance along the pattern to commence at.

Exemple

  • geom_to_wkt(apply_dash_pattern(geom_from_wkt('LINESTRING(1 1, 10 1)'), array(3, 1))) → MultiLineString ((1 1, 4 1),(5 1, 8 1),(9 1, 10 1, 10 1))

  • geom_to_wkt(apply_dash_pattern(geom_from_wkt('LINESTRING(1 1, 10 1)'), array(3, 1), start_rule:='half_dash')) → MultiLineString ((1 1, 2.5 1),(3.5 1, 6.5 1),(7.5 1, 10 1, 10 1))

13.2.13.4. $area

Returns the area of the current feature. The area calculated by this function respects both the current project’s ellipsoid setting and area unit settings. For example, if an ellipsoid has been set for the project then the calculated area will be ellipsoidal, and if no ellipsoid is set then the calculated area will be planimetric.

Sintaxă

$area

Exemple

  • $area → 42

13.2.13.5. area

Returns the area of a geometry polygon object. Calculations are always planimetric in the Spatial Reference System (SRS) of this geometry, and the units of the returned area will match the units for the SRS. This differs from the calculations performed by the $area function, which will perform ellipsoidal calculations based on the project’s ellipsoid and area unit settings.

Sintaxă

area(geometry)

Argumente

  • geometry - polygon geometry object

Exemple

  • area(geom_from_wkt('POLYGON((0 0, 4 0, 4 2, 0 2, 0 0))')) → 8.0

13.2.13.6. azimuth

Returns the north-based azimuth as the angle in radians measured clockwise from the vertical on point_a to point_b.

Sintaxă

azimuth(point_a, point_b)

Argumente

  • point_a - point geometry

  • point_b - point geometry

Exemple

  • degrees( azimuth( make_point(25, 45), make_point(75, 100) ) ) → 42.273689

  • degrees( azimuth( make_point(75, 100), make_point(25,45) ) ) → 222.273689

13.2.13.7. bearing

Returns the north-based bearing as the angle in radians measured clockwise on the ellipsoid from the vertical on point_a to point_b.

Sintaxă

bearing(point_a, point_b, [source_crs], [ellipsoid])

[] marks optional arguments

Argumente

  • point_a - point geometry

  • point_b - point geometry

  • source_crs - an optional string representing the source CRS of the points. By default the current layer’s CRS is used.

  • ellipsoid - an optional string representing the acronym or the authority:ID (eg «EPSG:7030») of the ellipsoid on which the bearing should be measured. By default the current project’s ellipsoid setting is used.

Exemple

  • degrees( bearing( make_point(16198544, -4534850), make_point(18736872, -1877769), 'EPSG:3857', 'EPSG:7030') ) → 49.980071

  • degrees( bearing( make_point(18736872, -1877769), make_point(16198544, -4534850), 'EPSG:3857', 'WGS84') ) → 219.282386

13.2.13.8. boundary

Returns the closure of the combinatorial boundary of the geometry (ie the topological boundary of the geometry). For instance, a polygon geometry will have a boundary consisting of the linestrings for each ring in the polygon. Some geometry types do not have a defined boundary, e.g., points or geometry collections, and will return NULL.

Sintaxă

boundary(geometry)

Argumente

  • geometry - a geometry

Exemple

  • geom_to_wkt(boundary(geom_from_wkt('Polygon((1 1, 0 0, -1 1, 1 1))'))) → «LineString(1 1,0 0,-1 1,1 1)»

  • geom_to_wkt(boundary(geom_from_wkt('LineString(1 1,0 0,-1 1)'))) → «MultiPoint ((1 1),(-1 1))»

../../../_images/boundary_polygon.png

Fig. 13.5 Boundary (black dashed line) of the source polygon layer

Mai multe detalii: Boundary algorithm

13.2.13.9. bounds

Returns a geometry which represents the bounding box of an input geometry. Calculations are in the Spatial Reference System of this geometry.

Sintaxă

bounds(geometry)

Argumente

  • geometry - a geometry

Exemple

  • bounds(@geometry) → bounding box of the current feature’s geometry

  • geom_to_wkt(bounds(geom_from_wkt('Polygon((1 1, 0 0, -1 1, 1 1))'))) → «Polygon ((-1 0, 1 0, 1 1, -1 1, -1 0))»

../../../_images/bounding_box.png

Fig. 13.6 Black lines represent the bounding boxes of each polygon feature

Mai multe detalii: Bounding boxes algorithm

13.2.13.10. bounds_height

Returns the height of the bounding box of a geometry. Calculations are in the Spatial Reference System of this geometry.

Sintaxă

bounds_height(geometry)

Argumente

  • geometry - a geometry

Exemple

  • bounds_height(@geometry) → height of bounding box of the current feature’s geometry

  • bounds_height(geom_from_wkt('Polygon((1 1, 0 0, -1 1, 1 1))')) → 1

13.2.13.11. bounds_width

Returns the width of the bounding box of a geometry. Calculations are in the Spatial Reference System of this geometry.

Sintaxă

bounds_width(geometry)

Argumente

  • geometry - a geometry

Exemple

  • bounds_width(@geometry) → width of bounding box of the current feature’s geometry

  • bounds_width(geom_from_wkt('Polygon((1 1, 0 0, -1 1, 1 1))')) → 2

13.2.13.12. buffer

Returns a geometry that represents all points whose distance from this geometry is less than or equal to distance. Calculations are in the Spatial Reference System of this geometry.

Sintaxă

buffer(geometry, distance, [segments=8], [cap=»round»], [join=»round»], [miter_limit=2])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • distance - buffer distance in layer units

  • segments - number of segments to use to represent a quarter circle when a round join style is used. A larger number results in a smoother buffer with more nodes.

  • cap - end cap style for buffer. Valid values are «round», «flat» or «square»

  • join - join style for buffer. Valid values are «round», «bevel» or «miter».

  • miter_limit - miter distance limit, for use when the join style is set to «miter»

Exemple

  • buffer(@geometry, 10.5) → polygon of the current feature’s geometry buffered by 10.5 units

../../../_images/buffer1.png

Fig. 13.7 Buffer (in yellow) of points, line, polygon with positive buffer, and polygon with negative buffer

Mai multe detalii: Buffer algorithm

13.2.13.13. buffer_by_m

Creates a buffer along a line geometry where the buffer diameter varies according to the m-values at the line vertices.

Sintaxă

buffer_by_m(geometry, [segments=8])

[] marks optional arguments

Argumente

  • geometry - input geometry. Must be a (multi)line geometry with m values.

  • segments - number of segments to approximate quarter-circle curves in the buffer.

Exemple

  • buffer_by_m(geometry:=geom_from_wkt('LINESTRINGM(1 2 0.5, 4 2 0.2)'),segments:=8) → A variable width buffer starting with a diameter of 0.5 and ending with a diameter of 0.2 along the linestring geometry.

../../../_images/variable_buffer_m.png

Fig. 13.8 Buffering line features using the m value on the vertices

Mai multe detalii: Algoritmul Variable width buffer (by M value)

13.2.13.14. centroid

Returns the geometric center of a geometry.

Sintaxă

centroid(geometry)

Argumente

  • geometry - a geometry

Exemple

  • centroid(@geometry) → a point geometry

../../../_images/centroids1.png

Fig. 13.9 The red stars represent the centroids of the features of the input layer.

Mai multe detalii: Algoritmul Centroids

13.2.13.15. close_line

Returns a closed line string of the input line string by appending the first point to the end of the line, if it is not already closed. If the geometry is not a line string or multi line string then the result will be NULL.

Sintaxă

close_line(geometry)

Argumente

  • geometry - a line string geometry

Exemple

  • geom_to_wkt(close_line(geom_from_wkt('LINESTRING(0 0, 1 0, 1 1)'))) → «LineString (0 0, 1 0, 1 1, 0 0)»

  • geom_to_wkt(close_line(geom_from_wkt('LINESTRING(0 0, 1 0, 1 1, 0 0)'))) → «LineString (0 0, 1 0, 1 1, 0 0)»

13.2.13.16. closest_point

Returns the point on geometry1 that is closest to geometry2.

Sintaxă

closest_point(geometry1, geometry2)

Argumente

  • geometry1 - geometry to find closest point on

  • geometry2 - geometry to find closest point to

Exemple

  • geom_to_wkt(closest_point(geom_from_wkt('LINESTRING (20 80, 98 190, 110 180, 50 75 )'),geom_from_wkt('POINT(100 100)'))) → «Point(73.0769 115.384)»

13.2.13.17. collect_geometries

Collects a set of geometries into a multi-part geometry object.

List of arguments variant

Geometry parts are specified as separate arguments to the function.

Sintaxă

collect_geometries(geometry1, geometry2, …)

Argumente

  • geometry - a geometry

Exemple

  • geom_to_wkt(collect_geometries(make_point(1,2), make_point(3,4), make_point(5,6))) → «MultiPoint ((1 2),(3 4),(5 6))»

Array variant

Geometry parts are specified as an array of geometry parts.

Sintaxă

collect_geometries(array)

Argumente

  • array - array of geometry objects

Exemple

  • geom_to_wkt(collect_geometries(array(make_point(1,2), make_point(3,4), make_point(5,6)))) → «MultiPoint ((1 2),(3 4),(5 6))»

Mai multe detalii: Algoritmul Collect geometries

13.2.13.18. combine

Returns the combination of two geometries.

Sintaxă

combine(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • geom_to_wkt( combine( geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ), geom_from_wkt( 'LINESTRING(3 3, 4 4, 2 1)' ) ) ) → «MULTILINESTRING((4 4, 2 1), (3 3, 4 4), (4 4, 5 5))»

  • geom_to_wkt( combine( geom_from_wkt( 'LINESTRING(3 3, 4 4)' ), geom_from_wkt( 'LINESTRING(3 3, 6 6, 2 1)' ) ) ) → «LINESTRING(3 3, 4 4, 6 6, 2 1)»

13.2.13.19. concave_hull

Returns a possibly concave polygon that contains all the points in the geometry

Sintaxă

concave_hull(geometry, target_percent, [allow_holes=False])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • target_percent - the percentage of area of the convex hull the solution tries to approach. A target_percent of 1 gives the same result as the convex hull. A target_percent between 0 and 0.99 produces a result that should have a smaller area than the convex hull.

  • allow_holes - optional argument specifying whether to allow holes within the output geometry. Defaults to FALSE, set to TRUE to avoid including holes in the output geometry.

Exemple

  • geom_to_wkt(concave_hull(geom_from_wkt('MULTILINESTRING((106 164,30 112,74 70,82 112,130 94,130 62,122 40,156 32,162 76,172 88),(132 178,134 148,128 136,96 128,132 108,150 130,170 142,174 110,156 96,158 90,158 88),(22 64,66 28,94 38,94 68,114 76,112 30,132 10,168 18,178 34,186 52,184 74,190 100,190 122,182 148,178 170,176 184,156 164,146 178,132 186,92 182,56 158,36 150,62 150,76 128,88 118))'), 0.99)) → «Polygon ((30 112, 36 150, 92 182, 132 186, 176 184, 190 122, 190 100, 186 52, 178 34, 168 18, 132 10, 112 30, 66 28, 22 64, 30 112))»

../../../_images/concave_hull_threshold.png

Concave hulls with increasing target_percent parameter

Further reading: convex_hull, Concave hull algorithm

13.2.13.20. contains

Tests whether a geometry contains another. Returns TRUE if and only if no points of geometry2 lie in the exterior of geometry1, and at least one point of the interior of geometry2 lies in the interior of geometry1.

Sintaxă

contains(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • contains( geom_from_wkt( 'POLYGON((0 0, 0 1, 1 1, 1 0, 0 0))' ), geom_from_wkt( 'POINT(0.5 0.5 )' ) ) → TRUE

  • contains( geom_from_wkt( 'POLYGON((0 0, 0 1, 1 1, 1 0, 0 0))' ), geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ) ) → FALSE

Mai multe detalii: overlay_contains

13.2.13.21. convex_hull

Returns the convex hull of a geometry. It represents the minimum convex geometry that encloses all geometries within the set.

Sintaxă

convex_hull(geometry)

Argumente

  • geometry - a geometry

Exemple

  • geom_to_wkt( convex_hull( geom_from_wkt( 'LINESTRING(3 3, 4 4, 4 10)' ) ) ) → «POLYGON((3 3, 4 10, 4 4, 3 3))»

../../../_images/convex_hull.png

Black lines identify the convex hull for each feature

Mai multe detalii: concave_hull, Convex hull algorithm

13.2.13.22. crosses

Tests whether a geometry crosses another. Returns TRUE if the supplied geometries have some, but not all, interior points in common.

Sintaxă

crosses(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • crosses( geom_from_wkt( 'LINESTRING(3 5, 4 4, 5 3)' ), geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ) ) → TRUE

  • crosses( geom_from_wkt( 'POINT(4 5)' ), geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ) ) → FALSE

Mai multe detalii: overlay_crosses

13.2.13.23. densify_by_count

Takes a polygon or line layer geometry and generates a new one in which the geometries have a larger number of vertices than the original one.

Sintaxă

densify_by_count(geometry, vertices)

Argumente

  • geometry - a geometry (accepts (multi)linestrings or (multi)polygons).

  • vertices - number of vertices to add (per segment)

Exemple

  • geom_to_wkt(densify_by_count(geom_from_wkt('LINESTRING(1 1, 10 1)'), 3)) → LineString (1 1, 3.25 1, 5.5 1, 7.75 1, 10 1)

../../../_images/densify_geometry.png

Red points show the vertices before and after the densify

Mai multe detalii: Densify by count algorithm

13.2.13.24. densify_by_distance

Takes a polygon or line layer geometry and generates a new one in which the geometries are densified by adding additional vertices on edges that have a maximum distance of the specified interval distance.

Sintaxă

densify_by_distance(geometry, distance)

Argumente

  • geometry - a geometry (accepts (multi)linestrings or (multi)polygons).

  • distance - maximum interval distance between vertices in output geometry

Exemple

  • geom_to_wkt(densify_by_distance(geom_from_wkt('LINESTRING(1 1, 10 1)'), 4)) → LineString (1 1, 4 1, 7 1, 10 1)

../../../_images/densify_geometry_interval.png

Densify geometry at a given interval

Mai multe detalii: Densify by interval algorithm

13.2.13.25. difference

Returns a geometry that represents that part of geometry1 that does not intersect with geometry2.

Sintaxă

difference(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • geom_to_wkt( difference( geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ), geom_from_wkt( 'LINESTRING(3 3, 4 4)' ) ) ) → «LINESTRING(4 4, 5 5)»

Mai multe detalii: Algoritmul Difference

13.2.13.26. disjoint

Tests whether geometries do not spatially intersect. Returns TRUE if the geometries do not share any space together.

Sintaxă

disjoint(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • disjoint( geom_from_wkt( 'POLYGON((0 0, 0 1, 1 1, 1 0, 0 0 ))' ), geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ) ) → TRUE

  • disjoint( geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ), geom_from_wkt( 'POINT(4 4)' )) → FALSE

Mai multe detalii: overlay_disjoint

13.2.13.27. distance

Returns the minimum distance (based on spatial reference) between two geometries in projected units.

Sintaxă

distance(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • distance( geom_from_wkt( 'POINT(4 4)' ), geom_from_wkt( 'POINT(4 8)' ) ) → 4

13.2.13.28. distance_to_vertex

Returns the distance along the geometry to a specified vertex.

Sintaxă

distance_to_vertex(geometry, vertex)

Argumente

  • geometry - a linestring geometry

  • vertex - vertex index, starting from 0; if the value is negative, the selected vertex index will be its total count minus the absolute value

Exemple

  • distance_to_vertex(geometry:=geom_from_wkt('LineString(0 0, 10 0, 10 10)'),vertex:=1) → 10.0

13.2.13.29. end_point

Returns the last node from a geometry.

Sintaxă

end_point(geometry)

Argumente

  • geometry - geometry object

Exemple

  • geom_to_wkt(end_point(geom_from_wkt('LINESTRING(4 0, 4 2, 0 2)'))) → «Point (0 2)»

../../../_images/end_point.png

End point of a line feature

Further reading: start_point, Extract specific vertices algorithm

13.2.13.30. exif_geotag

Creates a point geometry from the exif geotags of an image file.

Sintaxă

exif_geotag(path)

Argumente

  • cale - O cale a unui fișier de tip imagine sau o valoare a unui strat de hartă. Dacă este specificată o valoare a unui strat de hartă, atunci se va folosi sursa fișierului stratului.

Exemple

  • geom_to_wkt(exif_geotag('/my/photo.jpg')) → «Point (2 4)»

13.2.13.31. extend

Extends the start and end of a linestring geometry by a specified amount. Lines are extended using the bearing of the first and last segment in the line. For a multilinestring, all the parts are extended. Distances are in the Spatial Reference System of this geometry.

Sintaxă

extend(geometry, start_distance, end_distance)

Argumente

  • geometry - a (multi)linestring geometry

  • start_distance - distance to extend the start of the line

  • end_distance - distance to extend the end of the line.

Exemple

  • geom_to_wkt(extend(geom_from_wkt('LineString(0 0, 1 0, 1 1)'),1,2)) → «LineString (-1 0, 1 0, 1 3)»

  • geom_to_wkt(extend(geom_from_wkt('MultiLineString((0 0, 1 0, 1 1), (2 2, 0 2, 0 5))'),1,2)) → «MultiLineString ((-1 0, 1 0, 1 3),(3 2, 0 2, 0 7))»

../../../_images/extend_lines.png

The red dashes represent the initial and final extension of the original layer

Mai multe detalii: Algoritmul Extend lines

13.2.13.32. exterior_ring

Returns a line string representing the exterior ring of a polygon geometry. If the geometry is not a polygon then the result will be NULL.

Sintaxă

exterior_ring(geometry)

Argumente

  • geometry - a polygon geometry

Exemple

  • geom_to_wkt(exterior_ring(geom_from_wkt('POLYGON((-1 -1, 4 0, 4 2, 0 2, -1 -1),( 0.1 0.1, 0.1 0.2, 0.2 0.2, 0.2, 0.1, 0.1 0.1))'))) → «LineString (-1 -1, 4 0, 4 2, 0 2, -1 -1)»

../../../_images/exterior_ring.png

The dashed line represents the exterior ring of the polygon

13.2.13.33. extrude

Returns an extruded version of the input (Multi-)Curve or (Multi-)Linestring geometry with an extension specified by x and y.

Sintaxă

extrude(geometry, x, y)

Argumente

  • geometry - a curve or linestring geometry

  • x - x extension, numeric value

  • y - y extension, numeric value

Exemple

  • geom_to_wkt(extrude(geom_from_wkt('LineString(1 2, 3 2, 4 3)'), 1, 2)) → «Polygon ((1 2, 3 2, 4 3, 5 5, 4 4, 2 4, 1 2))»

  • geom_to_wkt(extrude(geom_from_wkt('MultiLineString((1 2, 3 2), (4 3, 8 3))'), 1, 2)) → «MultiPolygon (((1 2, 3 2, 4 4, 2 4, 1 2)),((4 3, 8 3, 9 5, 5 5, 4 3)))»

../../../_images/extrude.png

Generating a polygon by extruding a line with offset in x and y directions

13.2.13.34. flip_coordinates

Returns a copy of the geometry with the x and y coordinates swapped. Useful for repairing geometries which have had their latitude and longitude values reversed.

Sintaxă

flip_coordinates(geometry)

Argumente

  • geometry - a geometry

Exemple

  • geom_to_wkt(flip_coordinates(make_point(1, 2))) → «Point (2 1)»

  • geom_to_wkt(flip_coordinates(geom_from_wkt('LineString(0 2, 1 0, 1 6)'))) → «LineString (2 0, 0 1, 6 1)»

Mai multe detalii: Algoritmul Swap X and Y coordinates

13.2.13.35. force_polygon_ccw

Forces a geometry to respect the convention where exterior rings are counter-clockwise, interior rings are clockwise.

Sintaxă

force_polygon_ccw(geometry)

Argumente

  • geometry - a geometry. Any non-polygon geometries are returned unchanged.

Exemple

  • geom_to_wkt(force_polygon_ccw(geometry:=geom_from_wkt('Polygon ((-1 -1, 0 2, 4 2, 4 0, -1 -1))'))) → «Polygon ((-1 -1, 4 0, 4 2, 0 2, -1 -1))»

Mai multe detalii: force_polygon_cw, force_rhr

13.2.13.36. force_polygon_cw

Forces a geometry to respect the convention where exterior rings are clockwise, interior rings are counter-clockwise.

Sintaxă

force_polygon_cw(geometry)

Argumente

  • geometry - a geometry. Any non-polygon geometries are returned unchanged.

Exemple

  • geom_to_wkt(force_polygon_cw(geometry:=geom_from_wkt('POLYGON((-1 -1, 4 0, 4 2, 0 2, -1 -1))'))) → «Polygon ((-1 -1, 0 2, 4 2, 4 0, -1 -1))»

Mai multe detalii: force_polygon_ccw, force_rhr

13.2.13.37. force_rhr

Forces a geometry to respect the Right-Hand-Rule, in which the area that is bounded by a polygon is to the right of the boundary. In particular, the exterior ring is oriented in a clockwise direction and the interior rings in a counter-clockwise direction. Due to the inconsistency in the definition of the Right-Hand-Rule in some contexts it is recommended to use the explicit force_polygon_cw function instead.

Sintaxă

force_rhr(geometry)

Argumente

  • geometry - a geometry. Any non-polygon geometries are returned unchanged.

Exemple

  • geom_to_wkt(force_rhr(geometry:=geom_from_wkt('POLYGON((-1 -1, 4 0, 4 2, 0 2, -1 -1))'))) → «Polygon ((-1 -1, 0 2, 4 2, 4 0, -1 -1))»

Mai multe detalii: Force right-hand-rule algorithm, force_polygon_ccw, force_polygon_cw

13.2.13.38. geom_from_gml

Returns a geometry from a GML representation of geometry.

Sintaxă

geom_from_gml(gml)

Argumente

  • gml - GML representation of a geometry as a string

Exemple

  • geom_from_gml('<gml:LineString srsName="EPSG:4326"><gml:coordinates>4,4 5,5 6,6</gml:coordinates></gml:LineString>') → a line geometry object

13.2.13.39. geom_from_wkb

Returns a geometry created from a Well-Known Binary (WKB) representation.

Sintaxă

geom_from_wkb(binary)

Argumente

  • binary - Well-Known Binary (WKB) representation of a geometry (as a binary blob)

Exemple

  • geom_from_wkb( geom_to_wkb( make_point(4,5) ) ) → a point geometry object

13.2.13.40. geom_from_wkt

Returns a geometry created from a Well-Known Text (WKT) representation.

Sintaxă

geom_from_wkt(text)

Argumente

  • text - Well-Known Text (WKT) representation of a geometry

Exemple

  • geom_from_wkt( 'POINT(4 5)' ) → a geometry object

13.2.13.41. geom_to_wkb

Returns the Well-Known Binary (WKB) representation of a geometry

Sintaxă

geom_to_wkb(geometry)

Argumente

  • geometry - a geometry

Exemple

  • geom_to_wkb( @geometry ) → binary blob containing a geometry object

13.2.13.42. geom_to_wkt

Returns the Well-Known Text (WKT) representation of the geometry without SRID metadata.

Sintaxă

geom_to_wkt(geometry, [precision=8])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • precision - numeric precision

Exemple

  • geom_to_wkt( make_point(6, 50) ) → «POINT(6 50)»

  • geom_to_wkt(centroid(geom_from_wkt('Polygon((1 1, 0 0, -1 1, 1 1))'))) → «POINT(0 0.66666667)»

  • geom_to_wkt(centroid(geom_from_wkt('Polygon((1 1, 0 0, -1 1, 1 1))')), 2) → «POINT(0 0.67)»

13.2.13.43. $geometry

Returns the geometry of the current feature. Can be used for processing with other functions. WARNING: This function is deprecated. It is recommended to use the replacement @geometry variable instead.

Sintaxă

$geometry

Exemple

  • geom_to_wkt( $geometry ) → «POINT(6 50)»

13.2.13.44. geometrie

Returns a feature’s geometry.

Sintaxă

geometry(feature)

Argumente

  • feature - a feature object

Exemple

  • geometry( @feature ) → the geometry of the current feature. Prefer using @geometry.

  • geom_to_wkt( geometry( get_feature_by_id( 'streets', 1 ) ) ) → the geometry in WKT of the feature with the id 1 on the layer „streets”, e.g. «POINT(6 50)»

  • intersects( @geometry, geometry( get_feature( 'streets', 'name', 'Main St.' ) ) ) → TRUE if the current feature spatially intersects the «Main St.» named feature in the „streets” layer

13.2.13.45. geometry_n

Returns a specific geometry from a geometry collection, or NULL if the input geometry is not a collection. Also returns a part from a multipart geometry.

Sintaxă

geometry_n(geometry, index)

Argumente

  • geometry - geometry collection

  • index - index of geometry to return, where 1 is the first geometry in the collection

Exemple

  • geom_to_wkt(geometry_n(geom_from_wkt('GEOMETRYCOLLECTION(POINT(0 1), POINT(0 0), POINT(1 0), POINT(1 1))'),3)) → «Point (1 0)»

13.2.13.46. geometry_type

Returns a string value describing the type of a geometry (Point, Line or Polygon)

Sintaxă

geometry_type(geometry)

Argumente

  • geometry - a geometry

Exemple

  • geometry_type( geom_from_wkt( 'LINESTRING(2 5, 3 6, 4 8)') ) → «Line»

  • geometry_type( geom_from_wkt( 'MULTILINESTRING((2 5, 3 6, 4 8), (1 1, 0 0))') ) → «Line»

  • geometry_type( geom_from_wkt( 'POINT(2 5)') ) → «Point»

  • geometry_type( geom_from_wkt( 'POLYGON((-1 -1, 4 0, 4 2, 0 2, -1 -1))') ) → «Polygon»

13.2.13.47. hausdorff_distance

Returns the Hausdorff distance between two geometries. This is basically a measure of how similar or dissimilar 2 geometries are, with a lower distance indicating more similar geometries.

The function can be executed with an optional densify fraction argument. If not specified, an approximation to the standard Hausdorff distance is used. This approximation is exact or close enough for a large subset of useful cases. Examples of these are:

  • computing distance between Linestrings that are roughly parallel to each other, and roughly equal in length. This occurs in matching linear networks.

  • Testing similarity of geometries.

If the default approximate provided by this method is insufficient, specify the optional densify fraction argument. Specifying this argument performs a segment densification before computing the discrete Hausdorff distance. The parameter sets the fraction by which to densify each segment. Each segment will be split into a number of equal-length subsegments, whose fraction of the total length is closest to the given fraction. Decreasing the densify fraction parameter will make the distance returned approach the true Hausdorff distance for the geometries.

Sintaxă

hausdorff_distance(geometry1, geometry2, [densify_fraction])

[] marks optional arguments

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

  • densify_fraction - densify fraction amount

Exemple

  • hausdorff_distance( geometry1:= geom_from_wkt('LINESTRING (0 0, 2 1)'),geometry2:=geom_from_wkt('LINESTRING (0 0, 2 0)')) → 2

  • hausdorff_distance( geom_from_wkt('LINESTRING (130 0, 0 0, 0 150)'),geom_from_wkt('LINESTRING (10 10, 10 150, 130 10)')) → 14.142135623

  • hausdorff_distance( geom_from_wkt('LINESTRING (130 0, 0 0, 0 150)'),geom_from_wkt('LINESTRING (10 10, 10 150, 130 10)'),0.5) → 70.0

13.2.13.48. inclination

Returns the inclination measured from the zenith (0) to the nadir (180) on point_a to point_b.

Sintaxă

inclination(point_a, point_b)

Argumente

  • point_a - point geometry

  • point_b - point geometry

Exemple

  • inclination( make_point( 5, 10, 0 ), make_point( 5, 10, 5 ) ) → 0.0

  • inclination( make_point( 5, 10, 0 ), make_point( 5, 10, 0 ) ) → 90.0

  • inclination( make_point( 5, 10, 0 ), make_point( 50, 100, 0 ) ) → 90.0

  • inclination( make_point( 5, 10, 0 ), make_point( 5, 10, -5 ) ) → 180.0

13.2.13.49. interior_ring_n

Returns a specific interior ring from a polygon geometry, or NULL if the geometry is not a polygon.

Sintaxă

interior_ring_n(geometry, index)

Argumente

  • geometry - polygon geometry

  • index - index of interior to return, where 1 is the first interior ring

Exemple

  • geom_to_wkt(interior_ring_n(geom_from_wkt('POLYGON((-1 -1, 4 0, 4 2, 0 2, -1 -1),(-0.1 -0.1, 0.4 0, 0.4 0.2, 0 0.2, -0.1 -0.1),(-1 -1, 4 0, 4 2, 0 2, -1 -1))'),1)) → «LineString (-0.1 -0.1, 0.4 0, 0.4 0.2, 0 0.2, -0.1 -0.1))»

13.2.13.50. intersection

Returns a geometry that represents the shared portion of two geometries.

Sintaxă

intersection(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • geom_to_wkt( intersection( geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ), geom_from_wkt( 'LINESTRING(3 3, 4 4)' ) ) ) → «LINESTRING(3 3, 4 4)»

  • geom_to_wkt( intersection( geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ), geom_from_wkt( 'MULTIPOINT(3.5 3.5, 4 5)' ) ) ) → «POINT(3.5 3.5)»

Mai multe detalii: Algoritmul Intersection

13.2.13.51. intersects

Tests whether a geometry intersects another. Returns TRUE if the geometries spatially intersect (share any portion of space) and false if they do not.

Sintaxă

intersects(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • intersects( geom_from_wkt( 'POINT(4 4)' ), geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ) ) → TRUE

  • intersects( geom_from_wkt( 'POINT(4 5)' ), geom_from_wkt( 'POINT(5 5)' ) ) → FALSE

Mai multe detalii: overlay_intersects

13.2.13.52. intersects_bbox

Tests whether a geometry’s bounding box overlaps another geometry’s bounding box. Returns TRUE if the geometries spatially intersect the bounding box defined and false if they do not.

Sintaxă

intersects_bbox(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • intersects_bbox( geom_from_wkt( 'POINT(4 5)' ), geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ) ) → TRUE

  • intersects_bbox( geom_from_wkt( 'POINT(6 5)' ), geom_from_wkt( 'POLYGON((3 3, 4 4, 5 5, 3 3))' ) ) → FALSE

13.2.13.53. is_closed

Returns TRUE if a line string is closed (start and end points are coincident), or false if a line string is not closed. If the geometry is not a line string then the result will be NULL.

Sintaxă

is_closed(geometry)

Argumente

  • geometry - a line string geometry

Exemple

  • is_closed(geom_from_wkt('LINESTRING(0 0, 1 1, 2 2)')) → FALSE

  • is_closed(geom_from_wkt('LINESTRING(0 0, 1 1, 2 2, 0 0)')) → TRUE

13.2.13.54. is_empty

Returns TRUE if a geometry is empty (without coordinates), false if the geometry is not empty and NULL if there is no geometry. See also is_empty_or_null.

Sintaxă

is_empty(geometry)

Argumente

  • geometry - a geometry

Exemple

  • is_empty(geom_from_wkt('LINESTRING(0 0, 1 1, 2 2)')) → FALSE

  • is_empty(geom_from_wkt('LINESTRING EMPTY')) → TRUE

  • is_empty(geom_from_wkt('POINT(7 4)')) → FALSE

  • is_empty(geom_from_wkt('POINT EMPTY')) → TRUE

Mai multe detalii: is_empty_or_null

13.2.13.55. is_empty_or_null

Returns TRUE if a geometry is NULL or empty (without coordinates) or false otherwise. This function is like the expression «@geometry IS NULL or is_empty(@geometry)»

Sintaxă

is_empty_or_null(geometry)

Argumente

  • geometry - a geometry

Exemple

  • is_empty_or_null(NULL) → TRUE

  • is_empty_or_null(geom_from_wkt('LINESTRING(0 0, 1 1, 2 2)')) → FALSE

  • is_empty_or_null(geom_from_wkt('LINESTRING EMPTY')) → TRUE

  • is_empty_or_null(geom_from_wkt('POINT(7 4)')) → FALSE

  • is_empty_or_null(geom_from_wkt('POINT EMPTY')) → TRUE

Mai multe detalii: is_empty, NULL

13.2.13.56. is_multipart

Returns TRUE if the geometry is of Multi type.

Sintaxă

is_multipart(geometry)

Argumente

  • geometry - a geometry

Exemple

  • is_multipart(geom_from_wkt('MULTIPOINT ((0 0),(1 1),(2 2))')) → TRUE

  • is_multipart(geom_from_wkt('POINT (0 0)')) → FALSE

13.2.13.57. is_valid

Returns TRUE if a geometry is valid; if it is well-formed in 2D according to the OGC rules.

Sintaxă

is_valid(geometry)

Argumente

  • geometry - a geometry

Exemple

  • is_valid(geom_from_wkt('LINESTRING(0 0, 1 1, 2 2, 0 0)')) → TRUE

  • is_valid(geom_from_wkt('LINESTRING(0 0)')) → FALSE

Mai multe detalii: make_valid, Check validity algorithm

13.2.13.58. $length

Returns the length of a linestring. If you need the length of a border of a polygon, use $perimeter instead. The length calculated by this function respects both the current project’s ellipsoid setting and distance unit settings. For example, if an ellipsoid has been set for the project then the calculated length will be ellipsoidal, and if no ellipsoid is set then the calculated length will be planimetric.

Sintaxă

$length

Exemple

  • $length → 42.4711

13.2.13.59. length

Returns the number of characters in a string or the length of a geometry linestring.

String variant

Returns the number of characters in a string.

Sintaxă

length(string)

Argumente

  • string - string to count length of

Exemple

  • length('hello') → 5

Geometry variant

Calculate the length of a geometry line object. Calculations are always planimetric in the Spatial Reference System (SRS) of this geometry, and the units of the returned length will match the units for the SRS. This differs from the calculations performed by the $length function, which will perform ellipsoidal calculations based on the project’s ellipsoid and distance unit settings.

Sintaxă

length(geometry)

Argumente

  • geometry - line geometry object

Exemple

  • length(geom_from_wkt('LINESTRING(0 0, 4 0)')) → 4.0

Mai multe detalii: straight_distance_2d

13.2.13.60. length3D

Calculates the 3D length of a geometry line object. If the geometry is not a 3D line object, it returns its 2D length. Calculations are always planimetric in the Spatial Reference System (SRS) of this geometry, and the units of the returned length will match the units for the SRS. This differs from the calculations performed by the $length function, which will perform ellipsoidal calculations based on the project’s ellipsoid and distance unit settings.

Sintaxă

length3D(geometry)

Argumente

  • geometry - line geometry object

Exemple

  • length3D(geom_from_wkt('LINESTRINGZ(0 0 0, 3 0 4)')) → 5.0

13.2.13.61. line_interpolate_angle

Returns the angle parallel to the geometry at a specified distance along a linestring geometry. Angles are in degrees clockwise from north.

Sintaxă

line_interpolate_angle(geometry, distance)

Argumente

  • geometry - a linestring geometry

  • distance - distance along line to interpolate angle at

Exemple

  • line_interpolate_angle(geometry:=geom_from_wkt('LineString(0 0, 10 0)'),distance:=5) → 90.0

13.2.13.62. line_interpolate_point

Returns the point interpolated by a specified distance along a linestring geometry.

Sintaxă

line_interpolate_point(geometry, distance)

Argumente

  • geometry - a linestring geometry

  • distance - distance along line to interpolate

Exemple

  • geom_to_wkt(line_interpolate_point(geometry:=geom_from_wkt('LineString(0 0, 8 0)'), distance:=5)) → «Point (5 0)»

  • geom_to_wkt(line_interpolate_point(geometry:=geom_from_wkt('LineString(0 0, 1 1, 2 0)'), distance:=2.1)) → «Point (1.48492424 0.51507576)»

  • geom_to_wkt(line_interpolate_point(geometry:=geom_from_wkt('LineString(0 0, 1 0)'), distance:=2)) → NULL

../../../_images/interpolated_point.png

Interpolated point at 500m of the beginning of the line

Mai multe detalii: Algoritmul Interpolate point on line

13.2.13.63. line_locate_point

Returns the distance along a linestring corresponding to the closest position the linestring comes to a specified point geometry.

Sintaxă

line_locate_point(geometry, point)

Argumente

  • geometry - a linestring geometry

  • point - point geometry to locate closest position on linestring to

Exemple

  • line_locate_point(geometry:=geom_from_wkt('LineString(0 0, 10 0)'),point:=geom_from_wkt('Point(5 0)')) → 5.0

13.2.13.64. line_merge

Returns a LineString or MultiLineString geometry, where any connected LineStrings from the input geometry have been merged into a single linestring. This function will return NULL if passed a geometry which is not a LineString/MultiLineString.

Sintaxă

line_merge(geometry)

Argumente

  • geometry - a LineString/MultiLineString geometry

Exemple

  • geom_to_wkt(line_merge(geom_from_wkt('MULTILINESTRING((0 0, 1 1),(1 1, 2 2))'))) → «LineString(0 0,1 1,2 2)»

  • geom_to_wkt(line_merge(geom_from_wkt('MULTILINESTRING((0 0, 1 1),(11 1, 21 2))'))) → «MultiLineString((0 0, 1 1),(11 1, 21 2)»

13.2.13.65. line_substring

Returns the portion of a line (or curve) geometry which falls between the specified start and end distances (measured from the beginning of the line). Z and M values are linearly interpolated from existing values.

Sintaxă

line_substring(geometry, start_distance, end_distance)

Argumente

  • geometry - a linestring or curve geometry

  • start_distance - distance to start of substring

  • end_distance - distance to end of substring

Exemple

  • geom_to_wkt(line_substring(geometry:=geom_from_wkt('LineString(0 0, 10 0)'),start_distance:=2,end_distance:=6)) → «LineString (2 0,6 0)»

../../../_images/substring.png

Substring line with starting distance set at 0 meters and the ending distance at 250 meters.

Mai multe detalii: Algoritmul Line substring

13.2.13.66. m

Returns the m (measure) value of a point geometry.

Sintaxă

m(geometry)

Argumente

  • geometry - a point geometry

Exemple

  • m( geom_from_wkt( 'POINTM(2 5 4)' ) ) → 4

13.2.13.67. m_at

Retrieves a m coordinate of the geometry, or NULL if the geometry has no m value.

Sintaxă

m_at(geometry, vertex)

Argumente

  • geometry - geometry object

  • vertex - index of the vertex of the geometry (indices start at 0; negative values apply from the last index, starting at -1)

Exemple

  • m_at(geom_from_wkt('LineStringZM(0 0 0 0, 10 10 0 5, 10 10 0 0)'), 1) → 5

13.2.13.68. m_max

Returns the maximum m (measure) value of a geometry.

Sintaxă

m_max(geometry)

Argumente

  • geometry - a geometry containing m values

Exemple

  • m_max( make_point_m( 0,0,1 ) ) → 1

  • m_max(make_line( make_point_m( 0,0,1 ), make_point_m( -1,-1,2 ), make_point_m( -2,-2,0 ) ) ) → 2

13.2.13.69. m_min

Returns the minimum m (measure) value of a geometry.

Sintaxă

m_min(geometry)

Argumente

  • geometry - a geometry containing m values

Exemple

  • m_min( make_point_m( 0,0,1 ) ) → 1

  • m_min(make_line( make_point_m( 0,0,1 ), make_point_m( -1,-1,2 ), make_point_m( -2,-2,0 ) ) ) → 0

13.2.13.70. main_angle

Returns the angle of the long axis (clockwise, in degrees from North) of the oriented minimal bounding rectangle, which completely covers the geometry.

Sintaxă

main_angle(geometry)

Argumente

  • geometry - a geometry

Exemple

  • main_angle(geom_from_wkt('Polygon ((321577 129614, 321581 129618, 321585 129615, 321581 129610, 321577 129614))')) → 38.66

13.2.13.71. make_circle

Creates a circular polygon.

Sintaxă

make_circle(center, radius, [segments=36])

[] marks optional arguments

Argumente

  • center - center point of the circle

  • radius - radius of the circle

  • segments - optional argument for polygon segmentation. By default this value is 36

Exemple

  • geom_to_wkt(make_circle(make_point(10,10), 5, 4)) → «Polygon ((10 15, 15 10, 10 5, 5 10, 10 15))»

  • geom_to_wkt(make_circle(make_point(10,10,5), 5, 4)) → «PolygonZ ((10 15 5, 15 10 5, 10 5 5, 5 10 5, 10 15 5))»

  • geom_to_wkt(make_circle(make_point(10,10,5,30), 5, 4)) → «PolygonZM ((10 15 5 30, 15 10 5 30, 10 5 5 30, 5 10 5 30, 10 15 5 30))»

13.2.13.72. make_ellipse

Creates an elliptical polygon.

Sintaxă

make_ellipse(center, semi_major_axis, semi_minor_axis, azimuth, [segments=36])

[] marks optional arguments

Argumente

  • center - center point of the ellipse

  • semi_major_axis - semi-major axis of the ellipse

  • semi_minor_axis - semi-minor axis of the ellipse

  • azimuth - orientation of the ellipse

  • segments - optional argument for polygon segmentation. By default this value is 36

Exemple

  • geom_to_wkt(make_ellipse(make_point(10,10), 5, 2, 90, 4)) → «Polygon ((15 10, 10 8, 5 10, 10 12, 15 10))»

  • geom_to_wkt(make_ellipse(make_point(10,10,5), 5, 2, 90, 4)) → «PolygonZ ((15 10 5, 10 8 5, 5 10 5, 10 12 5, 15 10 5))»

  • geom_to_wkt(make_ellipse(make_point(10,10,5,30), 5, 2, 90, 4)) → «PolygonZM ((15 10 5 30, 10 8 5 30, 5 10 5 30, 10 12 5 30, 15 10 5 30))»

13.2.13.73. make_line

Creates a line geometry from a series of point geometries.

List of arguments variant

Line vertices are specified as separate arguments to the function.

Sintaxă

make_line(point1, point2, …)

Argumente

  • point - a point geometry (or array of points)

Exemple

  • geom_to_wkt(make_line(make_point(2,4),make_point(3,5))) → «LineString (2 4, 3 5)»

  • geom_to_wkt(make_line(make_point(2,4),make_point(3,5),make_point(9,7))) → «LineString (2 4, 3 5, 9 7)»

Array variant

Line vertices are specified as an array of points.

Sintaxă

make_line(array)

Argumente

  • array - array of points

Exemple

  • geom_to_wkt(make_line(array(make_point(2,4),make_point(3,5),make_point(9,7)))) → «LineString (2 4, 3 5, 9 7)»

13.2.13.74. make_point

Creates a point geometry from an x and y (and optional z and m) value.

Sintaxă

make_point(x, y, [z], [m])

[] marks optional arguments

Argumente

  • x - x coordinate of point

  • y - y coordinate of point

  • z - optional z coordinate of point

  • m - optional m value of point

Exemple

  • geom_to_wkt(make_point(2,4)) → «Point (2 4)»

  • geom_to_wkt(make_point(2,4,6)) → «PointZ (2 4 6)»

  • geom_to_wkt(make_point(2,4,6,8)) → «PointZM (2 4 6 8)»

13.2.13.75. make_point_m

Creates a point geometry from an x, y coordinate and m value.

Sintaxă

make_point_m(x, y, m)

Argumente

  • x - x coordinate of point

  • y - y coordinate of point

  • m - m value of point

Exemple

  • geom_to_wkt(make_point_m(2,4,6)) → «PointM (2 4 6)»

13.2.13.76. make_polygon

Creates a polygon geometry from an outer ring and optional series of inner ring geometries.

Sintaxă

make_polygon(outerRing, [innerRing1], [innerRing2], …)

[] marks optional arguments

Argumente

  • outerRing - closed line geometry for polygon’s outer ring

  • innerRing - optional closed line geometry for inner ring

Exemple

  • geom_to_wkt(make_polygon(geom_from_wkt('LINESTRING( 0 0, 0 1, 1 1, 1 0, 0 0 )'))) → «Polygon ((0 0, 0 1, 1 1, 1 0, 0 0))»

  • geom_to_wkt(make_polygon(geom_from_wkt('LINESTRING( 0 0, 0 1, 1 1, 1 0, 0 0 )'),geom_from_wkt('LINESTRING( 0.1 0.1, 0.1 0.2, 0.2 0.2, 0.2 0.1, 0.1 0.1 )'),geom_from_wkt('LINESTRING( 0.8 0.8, 0.8 0.9, 0.9 0.9, 0.9 0.8, 0.8 0.8 )'))) → «Polygon ((0 0, 0 1, 1 1, 1 0, 0 0),(0.1 0.1, 0.1 0.2, 0.2 0.2, 0.2 0.1, 0.1 0.1),(0.8 0.8, 0.8 0.9, 0.9 0.9, 0.9 0.8, 0.8 0.8))»

13.2.13.77. make_rectangle_3points

Creates a rectangle from 3 points.

Sintaxă

make_rectangle_3points(point1, point2, point3, [option=0])

[] marks optional arguments

Argumente

  • point1 - First point.

  • point2 - Second point.

  • point3 - Third point.

  • option - An optional argument to construct the rectangle. By default this value is 0. Value can be 0 (distance) or 1 (projected). Option distance: Second distance is equal to the distance between 2nd and 3rd point. Option projected: Second distance is equal to the distance of the perpendicular projection of the 3rd point on the segment or its extension.

Exemple

  • geom_to_wkt(make_rectangle_3points(make_point(0, 0), make_point(0,5), make_point(5, 5), 0)) → «Polygon ((0 0, 0 5, 5 5, 5 0, 0 0))»

  • geom_to_wkt(make_rectangle_3points(make_point(0, 0), make_point(0,5), make_point(5, 3), 1)) → «Polygon ((0 0, 0 5, 5 5, 5 0, 0 0))»

13.2.13.78. make_regular_polygon

Creates a regular polygon.

Sintaxă

make_regular_polygon(center, radius, number_sides, [circle=0])

[] marks optional arguments

Argumente

  • center - center of the regular polygon

  • radius - second point. The first if the regular polygon is inscribed. The midpoint of the first side if the regular polygon is circumscribed.

  • number_sides - Number of sides/edges of the regular polygon

  • circle - Optional argument to construct the regular polygon. By default this value is 0. Value can be 0 (inscribed) or 1 (circumscribed)

Exemple

  • geom_to_wkt(make_regular_polygon(make_point(0,0), make_point(0,5), 5)) → «Polygon ((0 5, 4.76 1.55, 2.94 -4.05, -2.94 -4.05, -4.76 1.55, 0 5))»

  • geom_to_wkt(make_regular_polygon(make_point(0,0), project(make_point(0,0), 4.0451, radians(36)), 5)) → «Polygon ((0 5, 4.76 1.55, 2.94 -4.05, -2.94 -4.05, -4.76 1.55, 0 5))»

13.2.13.79. make_square

Creates a square from a diagonal.

Sintaxă

make_square(point1, point2)

Argumente

  • point1 - First point of the diagonal

  • point2 - Last point of the diagonal

Exemple

  • geom_to_wkt(make_square( make_point(0,0), make_point(5,5))) → «Polygon ((0 0, -0 5, 5 5, 5 0, 0 0))»

  • geom_to_wkt(make_square( make_point(5,0), make_point(5,5))) → «Polygon ((5 0, 2.5 2.5, 5 5, 7.5 2.5, 5 0))»

13.2.13.80. make_triangle

Creates a triangle polygon.

Sintaxă

make_triangle(point1, point2, point3)

Argumente

  • point1 - first point of the triangle

  • point2 - second point of the triangle

  • point3 - third point of the triangle

Exemple

  • geom_to_wkt(make_triangle(make_point(0,0), make_point(5,5), make_point(0,10))) → «Triangle ((0 0, 5 5, 0 10, 0 0))»

  • geom_to_wkt(boundary(make_triangle(make_point(0,0), make_point(5,5), make_point(0,10)))) → «LineString (0 0, 5 5, 0 10, 0 0)»

13.2.13.81. make_valid

Returns a valid geometry or an empty geometry if the geometry could not be made valid.

Sintaxă

make_valid(geometry, [method=structure], [keep_collapsed=false])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • method - repair algorithm. May be either «structure» or «linework». The «linework» option combines all rings into a set of noded lines and then extracts valid polygons from that linework. The «structure» method first makes all rings valid and then merges shells and subtracts holes from shells to generate valid result. Assumes that holes and shells are correctly categorized.

  • keep_collapsed - if set to true, then components that have collapsed into a lower dimensionality will be kept. For example, a ring collapsing to a line, or a line collapsing to a point.

Exemple

  • geom_to_wkt(make_valid(geom_from_wkt('POLYGON((3 2, 4 1, 5 8, 3 2, 4 2))'))) → «Polygon ((3 2, 5 8, 4 1, 3 2))»

  • geom_to_wkt(make_valid(geom_from_wkt('POLYGON((3 2, 4 1, 5 8, 3 2, 4 2))'), 'linework')) → «GeometryCollection (Polygon ((5 8, 4 1, 3 2, 5 8)),LineString (3 2, 4 2))»

  • geom_to_wkt(make_valid(geom_from_wkt('POLYGON((3 2, 4 1, 5 8))'), method:='linework')) → «Polygon ((3 2, 4 1, 5 8, 3 2))»

  • make_valid(geom_from_wkt('LINESTRING(0 0)')) → An empty geometry

Mai multe detalii: is_valid, Fix geometries algorithm

13.2.13.82. minimal_circle

Returns the minimal enclosing circle of a geometry. It represents the minimum circle that encloses all geometries within the set.

Sintaxă

minimal_circle(geometry, [segments=36])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • segments - optional argument for polygon segmentation. By default this value is 36

Exemple

  • geom_to_wkt( minimal_circle( geom_from_wkt( 'LINESTRING(0 5, 0 -5, 2 1)' ), 4 ) ) → «Polygon ((0 5, 5 -0, -0 -5, -5 0, 0 5))»

  • geom_to_wkt( minimal_circle( geom_from_wkt( 'MULTIPOINT(1 2, 3 4, 3 2)' ), 4 ) ) → «Polygon ((3 4, 3 2, 1 2, 1 4, 3 4))»

../../../_images/minimum_enclosing_circles.png

Minimal enclosing circle of each feature

Mai multe detalii: Algoritmul Minimum enclosing circles

13.2.13.83. nodes_to_points

Returns a multipoint geometry consisting of every node in the input geometry.

Sintaxă

nodes_to_points(geometry, [ignore_closing_nodes=false])

[] marks optional arguments

Argumente

  • geometry - geometry object

  • ignore_closing_nodes - optional argument specifying whether to include duplicate nodes which close lines or polygons rings. Defaults to false, set to true to avoid including these duplicate nodes in the output collection.

Exemple

  • geom_to_wkt(nodes_to_points(geom_from_wkt('LINESTRING(0 0, 1 1, 2 2)'))) → «MultiPoint ((0 0),(1 1),(2 2))»

  • geom_to_wkt(nodes_to_points(geom_from_wkt('POLYGON((-1 -1, 4 0, 4 2, 0 2, -1 -1))'),true)) → «MultiPoint ((-1 -1),(4 0),(4 2),(0 2))»

../../../_images/extract_nodes.png

Multi-point feature extracted from vertices

Mai multe detalii: Algoritmul Extract vertices

13.2.13.84. num_geometries

Returns the number of geometries in a geometry collection, or the number of parts in a multi-part geometry. The function returns NULL if the input geometry is not a collection.

Sintaxă

num_geometries(geometry)

Argumente

  • geometry - geometry collection or multi-part geometry

Exemple

  • num_geometries(geom_from_wkt('GEOMETRYCOLLECTION(POINT(0 1), POINT(0 0), POINT(1 0), POINT(1 1))')) → 4

  • num_geometries(geom_from_wkt('MULTIPOINT((0 1), (0 0), (1 0))')) → 3

13.2.13.85. num_interior_rings

Returns the number of interior rings in a polygon or geometry collection, or NULL if the input geometry is not a polygon or collection.

Sintaxă

num_interior_rings(geometry)

Argumente

  • geometry - input geometry

Exemple

  • num_interior_rings(geom_from_wkt('POLYGON((-1 -1, 4 0, 4 2, 0 2, -1 -1),(-0.1 -0.1, 0.4 0, 0.4 0.2, 0 0.2, -0.1 -0.1))')) → 1

13.2.13.86. num_points

Returns the number of vertices in a geometry.

Sintaxă

num_points(geometry)

Argumente

  • geometry - a geometry

Exemple

  • num_points(@geometry) → number of vertices in the current feature’s geometry

13.2.13.87. num_rings

Returns the number of rings (including exterior rings) in a polygon or geometry collection, or NULL if the input geometry is not a polygon or collection.

Sintaxă

num_rings(geometry)

Argumente

  • geometry - input geometry

Exemple

  • num_rings(geom_from_wkt('POLYGON((-1 -1, 4 0, 4 2, 0 2, -1 -1),(-0.1 -0.1, 0.4 0, 0.4 0.2, 0 0.2, -0.1 -0.1))')) → 2

13.2.13.88. offset_curve

Returns a geometry formed by offsetting a linestring geometry to the side. Distances are in the Spatial Reference System of this geometry.

Sintaxă

offset_curve(geometry, distance, [segments=8], [join=1], [miter_limit=2.0])

[] marks optional arguments

Argumente

  • geometry - a (multi)linestring geometry

  • distance - offset distance. Positive values will be buffered to the left of lines, negative values to the right

  • segments - number of segments to use to represent a quarter circle when a round join style is used. A larger number results in a smoother line with more nodes.

  • join - join style for corners, where 1 = round, 2 = miter and 3 = bevel

  • miter_limit - limit on the miter ratio used for very sharp corners (when using miter joins only)

Exemple

  • offset_curve(@geometry, 10.5) → line offset to the left by 10.5 units

  • offset_curve(@geometry, -10.5) → line offset to the right by 10.5 units

  • offset_curve(@geometry, 10.5, segments:=16, join:=1) → line offset to the left by 10.5 units, using more segments to result in a smoother curve

  • offset_curve(@geometry, 10.5, join:=3) → line offset to the left by 10.5 units, using a beveled join

../../../_images/offset_lines.png

In blue the source layer, in red the offset one

Mai multe detalii: Algoritmul Offset lines

13.2.13.89. order_parts

Ordonează părțile unei MultiGeometrii după anumite criterii

Sintaxă

order_parts(geometry, orderby, [ascending=true])

[] marks optional arguments

Argumente

  • geometry - a multi-type geometry

  • orderby - an expression string defining the order criteria

  • ascending - boolean, True for ascending, False for descending

Exemple

  • geom_to_wkt(order_parts(geom_from_wkt('MultiPolygon (((1 1, 5 1, 5 5, 1 5, 1 1)),((1 1, 9 1, 9 9, 1 9, 1 1)))'), 'area(@geometry)', False)) → «MultiPolygon (((1 1, 9 1, 9 9, 1 9, 1 1)),((1 1, 5 1, 5 5, 1 5, 1 1)))»

  • geom_to_wkt(order_parts(geom_from_wkt('LineString(1 2, 3 2, 4 3)'), '1', True)) → «LineString(1 2, 3 2, 4 3)»

13.2.13.90. oriented_bbox

Returns a geometry which represents the minimal oriented bounding box of an input geometry.

Sintaxă

oriented_bbox(geometry)

Argumente

  • geometry - a geometry

Exemple

  • geom_to_wkt( oriented_bbox( geom_from_wkt( 'MULTIPOINT(1 2, 3 4, 3 2)' ) ) ) → «Polygon ((3 2, 3 4, 1 4, 1 2, 3 2))»

../../../_images/oriented_minimum_bounding_box.png

Oriented minimum bounding box

Mai multe detalii: Algoritmul Oriented minimum bounding box

13.2.13.91. overlaps

Tests whether a geometry overlaps another. Returns TRUE if the geometries share space, are of the same dimension, but are not completely contained by each other.

Sintaxă

overlaps(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • overlaps( geom_from_wkt( 'LINESTRING(3 5, 4 4, 5 5, 5 3)' ), geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ) ) → TRUE

  • overlaps( geom_from_wkt( 'LINESTRING(0 0, 1 1)' ), geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ) ) → FALSE

13.2.13.92. overlay_contains

Returns whether the current feature spatially contains at least one feature from a target layer, or an array of expression-based results for the features in the target layer contained in the current feature.

Read more on the underlying GEOS „Contains” predicate, as described in PostGIS ST_Contains function.

Sintaxă

overlay_contains(layer, [expression], [filter], [limit], [cache=false])

[] marks optional arguments

Argumente

  • layer - the layer whose overlay is checked

  • expression - an optional expression to evaluate on the features from the target layer. If not set, the function will just return a boolean indicating whether there is at least one match.

  • filter - an optional expression to filter the target features to check. If not set, all the features will be checked.

  • limit - an optional integer to limit the number of matching features. If not set, all the matching features will be returned.

  • cache - set this to true to build a local spatial index (most of the time, this is unwanted, unless you are working with a particularly slow data provider)

Exemple

  • overlay_contains('regions') → TRUE if the current feature spatially contains a region

  • overlay_contains('regions', filter:= population > 10000) → TRUE if the current feature spatially contains a region with a population greater than 10000

  • overlay_contains('regions', name) → an array of names, for the regions contained in the current feature

  • array_to_string(overlay_contains('regions', name)) → a string as a comma separated list of names, for the regions contained in the current feature

  • array_sort(overlay_contains(layer:='regions', expression:='name', filter:=population > 10000)) → o matrice ordonată după numele regiunilor conținute în entitatea curentă, și cu o populație de peste 10000 de locuitori

  • overlay_contains(layer:='regions', expression:= geom_to_wkt(@geometry), limit:=2) → an array of geometries (in WKT), for up to two regions contained in the current feature

Mai multe detalii: contains, manipularea matricilor, algoritmul Selectare după locație

13.2.13.93. overlay_crosses

Returns whether the current feature spatially crosses at least one feature from a target layer, or an array of expression-based results for the features in the target layer crossed by the current feature.

Read more on the underlying GEOS „Crosses” predicate, as described in PostGIS ST_Crosses function.

Sintaxă

overlay_crosses(layer, [expression], [filter], [limit], [cache=false])

[] marks optional arguments

Argumente

  • layer - the layer whose overlay is checked

  • expression - an optional expression to evaluate on the features from the target layer. If not set, the function will just return a boolean indicating whether there is at least one match.

  • filter - an optional expression to filter the target features to check. If not set, all the features will be checked.

  • limit - an optional integer to limit the number of matching features. If not set, all the matching features will be returned.

  • cache - set this to true to build a local spatial index (most of the time, this is unwanted, unless you are working with a particularly slow data provider)

Exemple

  • overlay_crosses('regions') → TRUE if the current feature spatially crosses a region

  • overlay_crosses('regions', filter:= population > 10000) → TRUE if the current feature spatially crosses a region with a population greater than 10000

  • overlay_crosses('regions', name) → an array of names, for the regions crossed by the current feature

  • array_to_string(overlay_crosses('regions', name)) → a string as a comma separated list of names, for the regions crossed by the current feature

  • array_sort(overlay_crosses(layer:='regions', expression:='name', filter:= population > 10000)) → o matrice ordonată după numele regiunilor traversate de entitatea curentă, și cu o populație de peste 10000 de locuitori

  • overlay_crosses(layer:='regions', expression:= geom_to_wkt(@geometry), limit:=2) → an array of geometries (in WKT), for up to two regions crossed by the current feature

Mai multe detalii: crosses, Gestionarea matricilor, Algoritmul Selectare după locație

13.2.13.94. overlay_disjoint

Returns whether the current feature is spatially disjoint from all the features of a target layer, or an array of expression-based results for the features in the target layer that are disjoint from the current feature.

Read more on the underlying GEOS „Disjoint” predicate, as described in PostGIS ST_Disjoint function.

Sintaxă

overlay_disjoint(layer, [expression], [filter], [limit], [cache=false])

[] marks optional arguments

Argumente

  • layer - the layer whose overlay is checked

  • expression - an optional expression to evaluate on the features from the target layer. If not set, the function will just return a boolean indicating whether there is at least one match.

  • filter - an optional expression to filter the target features to check. If not set, all the features will be checked.

  • limit - an optional integer to limit the number of matching features. If not set, all the matching features will be returned.

  • cache - set this to true to build a local spatial index (most of the time, this is unwanted, unless you are working with a particularly slow data provider)

Exemple

  • overlay_disjoint('regions') → TRUE if the current feature is spatially disjoint from all the regions

  • overlay_disjoint('regions', filter:= population > 10000) → TRUE if the current feature is spatially disjoint from all the regions with a population greater than 10000

  • overlay_disjoint('regions', name) → an array of names, for the regions spatially disjoint from the current feature

  • array_to_string(overlay_disjoint('regions', name)) → a string as a comma separated list of names, for the regions spatially disjoint from the current feature

  • array_sort(overlay_disjoint(layer:='regions', expression:='name', filter:=population > 10000)) → o matrice ordonată după numele regiunilor disjunse spațial de entitatea curentă, și cu o populație de peste 10000 de locuitori

  • overlay_disjoint(layer:='regions', expression:= geom_to_wkt(@geometry), limit:=2) → an array of geometries (in WKT), for up to two regions spatially disjoint from the current feature

Mai multe detalii: disjoint, Gestionarea matricilor, Algoritmul Selectare după locație

13.2.13.95. overlay_equals

Returns whether the current feature spatially equals to at least one feature from a target layer, or an array of expression-based results for the features in the target layer that are spatially equal to the current feature.

Read more on the underlying GEOS „Equals” predicate, as described in PostGIS ST_Equals function.

Sintaxă

overlay_equals(layer, [expression], [filter], [limit], [cache=false])

[] marks optional arguments

Argumente

  • layer - the layer whose overlay is checked

  • expression - an optional expression to evaluate on the features from the target layer. If not set, the function will just return a boolean indicating whether there is at least one match.

  • filter - an optional expression to filter the target features to check. If not set, all the features will be checked.

  • limit - an optional integer to limit the number of matching features. If not set, all the matching features will be returned.

  • cache - set this to true to build a local spatial index (most of the time, this is unwanted, unless you are working with a particularly slow data provider)

Exemple

  • overlay_equals('regions') → TRUE if the current feature is spatially equal to a region

  • overlay_equals('regions', filter:= population > 10000) → TRUE if the current feature is spatially equal to a region with a population greater than 10000

  • overlay_equals('regions', name) → an array of names, for the regions spatially equal to the current feature

  • array_to_string(overlay_equals('regions', name)) → a string as a comma separated list of names, for the regions spatially equal to the current feature

  • array_sort(overlay_equals(layer:='regions', expression:='name', filter:=population > 10000)) → o matrice ordonată după numele regiunilor egale spațial cu entitatea curentă, și cu o populație de peste 10000 de locuitori

  • overlay_equals(layer:='regions', expression:= geom_to_wkt(@geometry), limit:=2) → an array of geometries (in WKT), for up to two regions spatially equal to the current feature

Mai multe detalii: Gestionarea matricilor, Algoritmul Selectare după locație

13.2.13.96. overlay_intersects

Returns whether the current feature spatially intersects at least one feature from a target layer, or an array of expression-based results for the features in the target layer intersected by the current feature.

Read more on the underlying GEOS „Intersects” predicate, as described in PostGIS ST_Intersects function.

Sintaxă

overlay_intersects(layer, [expression], [filter], [limit], [cache=false], [min_overlap], [min_inscribed_circle_radius], [return_details], [sort_by_intersection_size])

[] marks optional arguments

Argumente

  • layer - the layer whose overlay is checked

  • expression - an optional expression to evaluate on the features from the target layer. If not set, the function will just return a boolean indicating whether there is at least one match.

  • filter - an optional expression to filter the target features to check. If not set, all the features will be checked.

  • limit - an optional integer to limit the number of matching features. If not set, all the matching features will be returned.

  • cache - set this to true to build a local spatial index (most of the time, this is unwanted, unless you are working with a particularly slow data provider)

  • min_overlap - defines an optional exclusion filter:

    • for polygons, a minimum area in current feature squared units for the intersection. If the intersection results in multiple polygons the intersection will be returned if at least one of the polygons has an area greater or equal to the value

    • for lines, a minimum length in current feature units. If the intersection results in multiple lines the intersection will be returned if at least one of the lines has a length greater or equal to the value.

  • min_inscribed_circle_radius - defines an optional exclusion filter (for polygons only): minimum radius in current feature units for the maximum inscribed circle of the intersection. If the intersection results in multiple polygons the intersection will be returned if at least one of the polygons has a radius for the maximum inscribed circle greater or equal to the value.

    Read more on the underlying GEOS predicate, as described in PostGIS ST_MaximumInscribedCircle function.

    This argument requires GEOS >= 3.9.

  • return_details - Set this to true to return a list of maps containing (key names in quotes) the feature «id», the expression «result» and the «overlap» value. The «radius» of the maximum inscribed circle is also returned when the target layer is a polygon. Only valid when used with the expression parameter

  • sort_by_intersection_size - only valid when used with an expression, set this to «des» to return the results ordered by the overlap value in descending order or set this to «asc» for ascending order.

Exemple

  • overlay_intersects('regions') → TRUE if the current feature spatially intersects a region

  • overlay_intersects('regions', filter:= population > 10000) → TRUE if the current feature spatially intersects a region with a population greater than 10000

  • overlay_intersects('regions', name) → an array of names, for the regions intersected by the current feature

  • array_to_string(overlay_intersects('regions', name)) → a string as a comma separated list of names, for the regions intersected by the current feature

  • array_sort(overlay_intersects(layer:='regions', expression:='name', filter:=population > 10000)) → o matrice ordonată după numele regiunilor intersectate de entitatea curentă, și cu o populație de peste 10000 de locuitori

  • overlay_intersects(layer:='regions', expression:= geom_to_wkt(@geometry), limit:=2) → an array of geometries (in WKT), for up to two regions intersected by the current feature

  • overlay_intersects(layer:='regions', min_overlap:=0.54) → TRUE if the current feature spatially intersects a region and the intersection area (of at least one of the parts in case of multipolygons) is greater or equal to 0.54

  • overlay_intersects(layer:='regions', min_inscribed_circle_radius:=0.54) → TRUE if the current feature spatially intersects a region and the intersection area maximum inscribed circle’s radius (of at least one of the parts in case of multipart) is greater or equal to 0.54

  • overlay_intersects(layer:='regions', expression:= geom_to_wkt(@geometry), return_details:=true) → an array of maps containing «id», «result», «overlap» and «radius»

  • overlay_intersects(layer:='regions', expression:= geom_to_wkt(@geometry), sort_by_intersection_size:='des') → an array of geometries (in WKT) ordered by the overlap value in descending order

Mai multe detalii: intersects, manipularea matricilor, algoritmul Selectare după locație

13.2.13.97. overlay_nearest

Returns whether the current feature has feature(s) from a target layer within a given distance, or an array of expression-based results for the features in the target layer within a distance from the current feature.

Note: This function can be slow and consume a lot of memory for large layers.

Sintaxă

overlay_nearest(layer, [expression], [filter], [limit=1], [max_distance], [cache=false])

[] marks optional arguments

Argumente

  • layer - the target layer

  • expression - an optional expression to evaluate on the features from the target layer. If not set, the function will just return a boolean indicating whether there is at least one match.

  • filter - an optional expression to filter the target features to check. If not set, all the features in the target layer will be used.

  • limit - an optional integer to limit the number of matching features. If not set, only the nearest feature will be returned. If set to -1, returns all the matching features.

  • max_distance - an optional distance to limit the search of matching features. If not set, all the features in the target layer will be used.

  • cache - set this to true to build a local spatial index (most of the time, this is unwanted, unless you are working with a particularly slow data provider)

Exemple

  • overlay_nearest('airports') → TRUE if the „airports” layer has at least one feature

  • overlay_nearest('airports', max_distance:= 5000) → TRUE if there is an airport within a distance of 5000 map units from the current feature

  • overlay_nearest('airports', name) → the name of the closest airport to the current feature, as an array

  • array_to_string(overlay_nearest('airports', name)) → the name of the closest airport to the current feature, as a string

  • overlay_nearest(layer:='airports', expression:= name, max_distance:= 5000) → numele celui mai apropiat aeroport, situat la o distanță de 5000 de unități de hartă față de entitatea curentă, sub formă de matrice

  • overlay_nearest(layer:='airports', expression:='name', filter:= 'Use'='Civil', limit:=3) → o matrice cu nume, pentru până la cele mai apropiate trei aeroporturi civile, ordonată după distanță

  • overlay_nearest(layer:='airports', expression:="name", limit:= -1, max_distance:= 5000) → an array of names, for all the airports within a distance of 5000 map units from the current feature, ordered by distance

Mai multe detalii: Gestionarea matricilor, Algoritmul Join attributes by nearest

13.2.13.98. overlay_touches

Returns whether the current feature spatially touches at least one feature from a target layer, or an array of expression-based results for the features in the target layer touched by the current feature.

Read more on the underlying GEOS „Touches” predicate, as described in PostGIS ST_Touches function.

Sintaxă

overlay_touches(layer, [expression], [filter], [limit], [cache=false])

[] marks optional arguments

Argumente

  • layer - the layer whose overlay is checked

  • expression - an optional expression to evaluate on the features from the target layer. If not set, the function will just return a boolean indicating whether there is at least one match.

  • filter - an optional expression to filter the target features to check. If not set, all the features will be checked.

  • limit - an optional integer to limit the number of matching features. If not set, all the matching features will be returned.

  • cache - set this to true to build a local spatial index (most of the time, this is unwanted, unless you are working with a particularly slow data provider)

Exemple

  • overlay_touches('regions') → TRUE if the current feature spatially touches a region

  • overlay_touches('regions', filter:= population > 10000) → TRUE if the current feature spatially touches a region with a population greater than 10000

  • overlay_touches('regions', name) → an array of names, for the regions touched by the current feature

  • string_to_array(overlay_touches('regions', name)) → a string as a comma separated list of names, for the regions touched by the current feature

  • array_sort(overlay_touches(layer:='regions', expression:='name', filter:=population > 10000)) → o matrice ordonată după numele regiunilor atinse de entitatea curentă, și cu o populație de peste 10000 de locuitori

  • overlay_touches(layer:='regions', expression:= geom_to_wkt(@geometry), limit:=2) → an array of geometries (in WKT), for up to two regions touched by the current feature

Mai multe detalii: touches, Gestionarea matricilor, Algoritmul Selectare după locație

13.2.13.99. overlay_within

Returns whether the current feature is spatially within at least one feature from a target layer, or an array of expression-based results for the features in the target layer that contain the current feature.

Read more on the underlying GEOS „Within” predicate, as described in PostGIS ST_Within function.

Sintaxă

overlay_within(layer, [expression], [filter], [limit], [cache=false])

[] marks optional arguments

Argumente

  • layer - the layer whose overlay is checked

  • expression - an optional expression to evaluate on the features from the target layer. If not set, the function will just return a boolean indicating whether there is at least one match.

  • filter - an optional expression to filter the target features to check. If not set, all the features will be checked.

  • limit - an optional integer to limit the number of matching features. If not set, all the matching features will be returned.

  • cache - set this to true to build a local spatial index (most of the time, this is unwanted, unless you are working with a particularly slow data provider)

Exemple

  • overlay_within('regions') → TRUE if the current feature is spatially within a region

  • overlay_within('regions', filter:= population > 10000) → TRUE if the current feature is spatially within a region with a population greater than 10000

  • overlay_within('regions', name) → an array of names, for the regions containing the current feature

  • array_to_string(overlay_within('regions', name)) → a string as a comma separated list of names, for the regions containing the current feature

  • array_sort(overlay_within(layer:='regions', expression:='name', filter:=population > 10000)) → o matrice ordonată după numele regiunilor care conțin entitatea curentă, și au o populație de peste 10000 de locuitori

  • overlay_within(layer:='regions', expression:= geom_to_wkt(@geometry), limit:=2) → an array of geometries (in WKT), for up to two regions containing the current feature

Mai multe detalii: within, Gestionarea matricilor, Algoritmul Selectare după locație

13.2.13.100. $perimeter

Returns the perimeter length of the current feature. The perimeter calculated by this function respects both the current project’s ellipsoid setting and distance unit settings. For example, if an ellipsoid has been set for the project then the calculated perimeter will be ellipsoidal, and if no ellipsoid is set then the calculated perimeter will be planimetric.

Sintaxă

$perimeter

Exemple

  • $perimeter → 42

13.2.13.101. perimeter

Returns the perimeter of a geometry polygon object. Calculations are always planimetric in the Spatial Reference System (SRS) of this geometry, and the units of the returned perimeter will match the units for the SRS. This differs from the calculations performed by the $perimeter function, which will perform ellipsoidal calculations based on the project’s ellipsoid and distance unit settings.

Sintaxă

perimeter(geometry)

Argumente

  • geometry - polygon geometry object

Exemple

  • perimeter(geom_from_wkt('POLYGON((0 0, 4 0, 4 2, 0 2, 0 0))')) → 12.0

13.2.13.102. point_n

Returns a specific node from a geometry.

Sintaxă

point_n(geometry, index)

Argumente

  • geometry - geometry object

  • index - index of node to return, where 1 is the first node; if the value is negative, the selected vertex index will be its total count minus the absolute value

Exemple

  • geom_to_wkt(point_n(geom_from_wkt('POLYGON((0 0, 4 0, 4 2, 0 2, 0 0))'),2)) → «Point (4 0)»

Mai multe detalii: Algoritmul Extract specific vertices

13.2.13.103. point_on_surface

Returns a point guaranteed to lie on the surface of a geometry.

Sintaxă

point_on_surface(geometry)

Argumente

  • geometry - a geometry

Exemple

  • point_on_surface(@geometry) → a point geometry

Mai multe detalii: Algoritmul Point on Surface

13.2.13.104. pole_of_inaccessibility

Calculates the approximate pole of inaccessibility for a surface, which is the most distant internal point from the boundary of the surface. This function uses the «polylabel» algorithm (Vladimir Agafonkin, 2016), which is an iterative approach guaranteed to find the true pole of inaccessibility within a specified tolerance. More precise tolerances require more iterations and will take longer to calculate.

Sintaxă

pole_of_inaccessibility(geometry, tolerance)

Argumente

  • geometry - a geometry

  • tolerance - maximum distance between the returned point and the true pole location

Exemple

  • geom_to_wkt(pole_of_inaccessibility( geom_from_wkt('POLYGON((0 1, 0 9, 3 10, 3 3, 10 3, 10 1, 0 1))'), 0.1)) → «Point(1.546875 2.546875)»

../../../_images/pole_inaccessibility.png

Pole of inaccessibility

Mai multe detalii: Algoritmul Pole of inaccessibility

13.2.13.105. proiect

Returns a point projected from a start point using a distance, a bearing (azimuth) and an elevation in radians.

Sintaxă

project(point, distance, azimuth, [elevation])

[] marks optional arguments

Argumente

  • point - start point

  • distance - distance to project

  • azimuth - azimuth in radians clockwise, where 0 corresponds to north

  • elevation - angle of inclination in radians

Exemple

  • geom_to_wkt(project(make_point(1, 2), 3, radians(270))) → «Point(-2, 2)»

Mai multe detalii: Algoritmul Project points (Cartesian)

13.2.13.106. relate

Tests the Dimensional Extended 9 Intersection Model (DE-9IM) representation of the relationship between two geometries.

Relationship variant

Returns the Dimensional Extended 9 Intersection Model (DE-9IM) representation of the relationship between two geometries.

Sintaxă

relate(geometry, geometry)

Argumente

  • geometry - a geometry

  • geometry - a geometry

Exemple

  • relate( geom_from_wkt( 'LINESTRING(40 40,120 120)' ), geom_from_wkt( 'LINESTRING(40 40,60 120)' ) ) → «FF1F00102»

Pattern match variant

Tests whether the DE-9IM relationship between two geometries matches a specified pattern.

Sintaxă

relate(geometry, geometry, pattern)

Argumente

  • geometry - a geometry

  • geometry - a geometry

  • pattern - DE-9IM pattern to match

Exemple

  • relate( geom_from_wkt( 'LINESTRING(40 40,120 120)' ), geom_from_wkt( 'LINESTRING(40 40,60 120)' ), '**1F001**' ) → TRUE

13.2.13.107. reverse

Reverses the direction of a line string by reversing the order of its vertices.

Sintaxă

reverse(geometry)

Argumente

  • geometry - a geometry

Exemple

  • geom_to_wkt(reverse(geom_from_wkt('LINESTRING(0 0, 1 1, 2 2)'))) → «LINESTRING(2 2, 1 1, 0 0)»

../../../_images/reverse_line.png

Reversing line direction

Mai multe detalii: Algoritmul Inversează sensul liniei

13.2.13.108. rotate

Returns a rotated version of a geometry. Calculations are in the Spatial Reference System of this geometry.

Sintaxă

rotate(geometry, rotation, [center=NULL], [per_part=false])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • rotation - clockwise rotation in degrees

  • center - rotation center point. If not specified, the center of the geometry’s bounding box is used.

  • per_part - apply rotation per part. If true, then rotation will apply around the center of each part’s bounding box when the input geometry is multipart and an explicit rotation center point is not specified.

Exemple

  • rotate(@geometry, 45, make_point(4, 5)) → geometry rotated 45 degrees clockwise around the (4, 5) point

  • rotate(@geometry, 45) → geometry rotated 45 degrees clockwise around the center of its bounding box

../../../_images/rotate.gif

Rotating features

13.2.13.109. roundness

Calculates how close a polygon shape is to a circle. The function Returns TRUE when the polygon shape is a perfect circle and 0 when it is completely flat.

Sintaxă

roundness(geometry)

Argumente

  • geometry - a polygon

Exemple

  • round(roundness(geom_from_wkt('POLYGON(( 0 0, 0 1, 1 1, 1 0, 0 0))')), 3) → 0.785

  • round(roundness(geom_from_wkt('POLYGON(( 0 0, 0 0.1, 1 0.1, 1 0, 0 0))')), 3) → 0.260

Mai multe detalii: Roundness algorithm

13.2.13.110. scale

Returns a scaled version of a geometry. Calculations are in the Spatial Reference System of this geometry.

Sintaxă

scale(geometry, x_scale, y_scale, [center])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • x_scale - x-axis scaling factor

  • y_scale - y-axis scaling factor

  • center - scaling center point. If not specified, the center of the geometry’s bounding box is used.

Exemple

  • scale(@geometry, 2, 0.5, make_point(4, 5)) → geometry scaled twice horizontally and halved vertically, around the (4, 5) point

  • scale(@geometry, 2, 0.5) → geometry twice horizontally and halved vertically, around the center of its bounding box

13.2.13.111. segments_to_lines

Returns a multi line geometry consisting of a line for every segment in the input geometry.

Sintaxă

segments_to_lines(geometry)

Argumente

  • geometry - geometry object

Exemple

  • geom_to_wkt(segments_to_lines(geom_from_wkt('LINESTRING(0 0, 1 1, 2 2)'))) → «MultiLineString ((0 0, 1 1),(1 1, 2 2))»

Mai multe detalii: Algoritmul Explode lines

13.2.13.112. shared_paths

Returns a collection containing paths shared by the two input geometries. Those going in the same direction are in the first element of the collection, those going in the opposite direction are in the second element. The paths themselves are given in the direction of the first geometry.

Sintaxă

shared_paths(geometry1, geometry2)

Argumente

  • geometry1 - a LineString/MultiLineString geometry

  • geometry2 - a LineString/MultiLineString geometry

Exemple

  • geom_to_wkt(shared_paths(geom_from_wkt('MULTILINESTRING((26 125,26 200,126 200,126 125,26 125),(51 150,101 150,76 175,51 150)))'),geom_from_wkt('LINESTRING(151 100,126 156.25,126 125,90 161, 76 175)'))) → «GeometryCollection (MultiLineString ((126 156.25, 126 125),(101 150, 90 161),(90 161, 76 175)),MultiLineString EMPTY)»

  • geom_to_wkt(shared_paths(geom_from_wkt('LINESTRING(76 175,90 161,126 125,126 156.25,151 100)'),geom_from_wkt('MULTILINESTRING((26 125,26 200,126 200,126 125,26 125),(51 150,101 150,76 175,51 150))'))) → «GeometryCollection (MultiLineString EMPTY,MultiLineString ((76 175, 90 161),(90 161, 101 150),(126 125, 126 156.25)))»

13.2.13.113. shortest_line

Returns the shortest line joining geometry1 to geometry2. The resultant line will start at geometry1 and end at geometry2.

Sintaxă

shortest_line(geometry1, geometry2)

Argumente

  • geometry1 - geometry to find shortest line from

  • geometry2 - geometry to find shortest line to

Exemple

  • geom_to_wkt(shortest_line(geom_from_wkt('LINESTRING (20 80, 98 190, 110 180, 50 75 )'),geom_from_wkt('POINT(100 100)'))) → «LineString(73.0769 115.384, 100 100)»

13.2.13.114. simplify

Simplifies a geometry by removing nodes using a distance based threshold (ie, the Douglas Peucker algorithm). The algorithm preserves large deviations in geometries and reduces the number of vertices in nearly straight segments.

Sintaxă

simplify(geometry, tolerance)

Argumente

  • geometry - a geometry

  • tolerance - maximum deviation from straight segments for points to be removed

Exemple

  • geom_to_wkt(simplify(geometry:=geom_from_wkt('LineString(0 0, 5 0.1, 10 0)'),tolerance:=5)) → «LineString(0 0, 10 0)»

../../../_images/simplify_geometries.png

From left to right, source layer and increasing simplification tolerances

Mai multe detalii: Algoritmul Simplify

13.2.13.115. simplify_vw

Simplifies a geometry by removing nodes using an area based threshold (ie, the Visvalingam-Whyatt algorithm). The algorithm removes vertices which create small areas in geometries, e.g., narrow spikes or nearly straight segments.

Sintaxă

simplify_vw(geometry, tolerance)

Argumente

  • geometry - a geometry

  • tolerance - a measure of the maximum area created by a node for the node to be removed

Exemple

  • geom_to_wkt(simplify_vw(geometry:=geom_from_wkt('LineString(0 0, 5 0, 5.01 10, 5.02 0, 10 0)'),tolerance:=5)) → «LineString(0 0, 10 0)»

Mai multe detalii: Algoritmul Simplify

13.2.13.116. single_sided_buffer

Returns a geometry formed by buffering out just one side of a linestring geometry. Distances are in the Spatial Reference System of this geometry.

Sintaxă

single_sided_buffer(geometry, distance, [segments=8], [join=1], [miter_limit=2.0])

[] marks optional arguments

Argumente

  • geometry - a (multi)linestring geometry

  • distance - buffer distance. Positive values will be buffered to the left of lines, negative values to the right

  • segments - number of segments to use to represent a quarter circle when a round join style is used. A larger number results in a smoother buffer with more nodes.

  • join - join style for corners, where 1 = round, 2 = miter and 3 = bevel

  • miter_limit - limit on the miter ratio used for very sharp corners (when using miter joins only)

Exemple

  • single_sided_buffer(@geometry, 10.5) → line buffered to the left by 10.5 units

  • single_sided_buffer(@geometry, -10.5) → line buffered to the right by 10.5 units

  • single_sided_buffer(@geometry, 10.5, segments:=16, join:=1) → line buffered to the left by 10.5 units, using more segments to result in a smoother buffer

  • single_sided_buffer(@geometry, 10.5, join:=3) → line buffered to the left by 10.5 units, using a beveled join

../../../_images/single_side_buffer.png

Left versus right side buffer on the same vector line layer

Mai multe detalii: Algoritmul Single sided buffer

13.2.13.117. sinuosity

Returns the sinuosity of a curve, which is the ratio of the curve length to the straight (2D) distance between its endpoints.

Sintaxă

sinuosity(geometry)

Argumente

  • geometry - Input curve (circularstring, linestring)

Exemple

  • round(sinuosity(geom_from_wkt('LINESTRING(2 0, 2 2, 3 2, 3 3)')), 3) → 1.265

  • sinuosity(geom_from_wkt('LINESTRING( 3 1, 5 1)')) → 1.0

13.2.13.118. smooth

Smooths a geometry by adding extra nodes which round off corners in the geometry. If input geometries contain Z or M values, these will also be smoothed and the output geometry will retain the same dimensionality as the input geometry.

Sintaxă

smooth(geometry, [iterations=1], [offset=0.25], [min_length=-1], [max_angle=180])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • iterations - number of smoothing iterations to apply. Larger numbers result in smoother but more complex geometries.

  • offset - value between 0 and 0.5 which controls how tightly the smoothed geometry follow the original geometry. Smaller values result in a tighter smoothing, larger values result in looser smoothing.

  • min_length - minimum length of segments to apply smoothing to. This parameter can be used to avoid placing excessive additional nodes in shorter segments of the geometry.

  • max_angle - maximum angle at node for smoothing to be applied (0-180). By lowering the maximum angle intentionally sharp corners in the geometry can be preserved. For instance, a value of 80 degrees will retain right angles in the geometry.

Exemple

  • geom_to_wkt(smooth(geometry:=geom_from_wkt('LineString(0 0, 5 0, 5 5)'),iterations:=1,offset:=0.2,min_length:=-1,max_angle:=180)) → «LineString (0 0, 4 0, 5 1, 5 5)»

../../../_images/smooth_geometry_1.png

Increasing number of iterations causes smoother geometries

Mai multe detalii: Algoritmul Smooth

13.2.13.119. square_wave

Constructs square/rectangular waves along the boundary of a geometry.

Sintaxă

square_wave(geometry, wavelength, amplitude, [strict=False])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • wavelength - wavelength of square waveform

  • amplitude - amplitude of square waveform

  • strict - By default the wavelength argument is treated as a „maximum wavelength”, where the actual wavelength will be dynamically adjusted so that an exact number of square waves are created along the boundaries of the geometry. If the strict argument is set to true then the wavelength will be used exactly and an incomplete pattern may be used for the final waveform.

Exemple

  • square_wave(geom_from_wkt('LineString(0 0, 10 0)'), 3, 1) → Square waves with wavelength 3 and amplitude 1 along the linestring

../../../_images/square_wave.png

Symbolizing features with square waves

13.2.13.120. square_wave_randomized

Constructs randomized square/rectangular waves along the boundary of a geometry.

Sintaxă

square_wave_randomized(geometry, min_wavelength, max_wavelength, min_amplitude, max_amplitude, [seed=0])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • min_wavelength - minimum wavelength of waves

  • max_wavelength - maximum wavelength of waves

  • min_amplitude - minimum amplitude of waves

  • max_amplitude - maximum amplitude of waves

  • seed - specifies a random seed for generating waves. If the seed is 0, then a completely random set of waves will be generated.

Exemple

  • square_wave_randomized(geom_from_wkt('LineString(0 0, 10 0)'), 2, 3, 0.1, 0.2) → Randomly sized square waves with wavelengths between 2 and 3 and amplitudes between 0.1 and 0.2 along the linestring

../../../_images/square_wave_randomized.png

Symbolizing features with square randomized waves

13.2.13.121. start_point

Returns the first node from a geometry.

Sintaxă

start_point(geometry)

Argumente

  • geometry - geometry object

Exemple

  • geom_to_wkt(start_point(geom_from_wkt('LINESTRING(4 0, 4 2, 0 2)'))) → «Point (4 0)»

../../../_images/start_point.png

Starting point of a line feature

Further reading: end_point, Extract specific vertices algorithm

13.2.13.122. straight_distance_2d

Returns the direct/euclidean distance between the first and last vertex of a geometry. The geometry must be a curve (circularstring, linestring).

Sintaxă

straight_distance_2d(geometry)

Argumente

  • geometry - The geometry.

Exemple

  • straight_distance_2d(geom_from_wkt('LINESTRING(1 0, 1 1)')) → 1

  • round(straight_distance_2d(geom_from_wkt('LINESTRING(1 4, 3 5, 5 0)')), 3) → 5.657

Mai multe detalii: length

13.2.13.123. sym_difference

Returns a geometry that represents the portions of two geometries that do not intersect.

Sintaxă

sym_difference(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • geom_to_wkt( sym_difference( geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ), geom_from_wkt( 'LINESTRING(3 3, 8 8)' ) ) ) → «LINESTRING(5 5, 8 8)»

Mai multe detalii: Algoritmul Symmetrical difference

13.2.13.124. tapered_buffer

Creates a buffer along a line geometry where the buffer diameter varies evenly over the length of the line.

Sintaxă

tapered_buffer(geometry, start_width, end_width, [segments=8])

[] marks optional arguments

Argumente

  • geometry - input geometry. Must be a (multi)line geometry.

  • start_width - width of buffer at start of line,

  • end_width - width of buffer at end of line.

  • segments - number of segments to approximate quarter-circle curves in the buffer.

Exemple

  • tapered_buffer(geometry:=geom_from_wkt('LINESTRING(1 2, 4 2)'),start_width:=1,end_width:=2,segments:=8) → A tapered buffer starting with a diameter of 1 and ending with a diameter of 2 along the linestring geometry.

../../../_images/tapered_buffer.png

Tapered buffer on line features

Mai multe detalii: Algoritmul Tapered buffers

13.2.13.125. touches

Tests whether a geometry touches another. Returns TRUE if the geometries have at least one point in common, but their interiors do not intersect.

Sintaxă

touches(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • touches( geom_from_wkt( 'LINESTRING(5 3, 4 4)' ), geom_from_wkt( 'LINESTRING(3 3, 4 4, 5 5)' ) ) → TRUE

  • touches( geom_from_wkt( 'POINT(4 4)' ), geom_from_wkt( 'POINT(5 5)' ) ) → FALSE

Mai multe detalii: overlay_touches

13.2.13.126. transform

Returns the geometry transformed from a source CRS to a destination CRS.

Sintaxă

transform(geometry, source_auth_id, dest_auth_id)

Argumente

  • geometry - a geometry

  • source_auth_id - the source auth CRS ID

  • dest_auth_id - the destination auth CRS ID

Exemple

  • geom_to_wkt( transform( make_point(488995.53240249, 7104473.38600835), 'EPSG:2154', 'EPSG:4326' ) ) → «POINT(0 51)»

Mai multe detalii: Algoritmul Reproject layer

13.2.13.127. translate

Returns a translated version of a geometry. Calculations are in the Spatial Reference System of this geometry.

Sintaxă

translate(geometry, dx, dy)

Argumente

  • geometry - a geometry

  • dx - delta x

  • dy - delta y

Exemple

  • translate(@geometry, 5, 10) → a geometry of the same type like the original one

../../../_images/translate_geometry.png

Translating features

Mai multe detalii: Algoritmul Translate

13.2.13.128. triangular_wave

Constructs triangular waves along the boundary of a geometry.

Sintaxă

triangular_wave(geometry, wavelength, amplitude, [strict=False])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • wavelength - wavelength of triangular waveform

  • amplitude - amplitude of triangular waveform

  • strict - By default the wavelength argument is treated as a „maximum wavelength”, where the actual wavelength will be dynamically adjusted so that an exact number of triangular waves are created along the boundaries of the geometry. If the strict argument is set to true then the wavelength will be used exactly and an incomplete pattern may be used for the final waveform.

Exemple

  • triangular_wave(geom_from_wkt('LineString(0 0, 10 0)'), 3, 1) → Triangular waves with wavelength 3 and amplitude 1 along the linestring

../../../_images/triangular_wave.png

Symbolizing features with triangular waves

13.2.13.129. triangular_wave_randomized

Constructs randomized triangular waves along the boundary of a geometry.

Sintaxă

triangular_wave_randomized(geometry, min_wavelength, max_wavelength, min_amplitude, max_amplitude, [seed=0])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • min_wavelength - minimum wavelength of waves

  • max_wavelength - maximum wavelength of waves

  • min_amplitude - minimum amplitude of waves

  • max_amplitude - maximum amplitude of waves

  • seed - specifies a random seed for generating waves. If the seed is 0, then a completely random set of waves will be generated.

Exemple

  • triangular_wave_randomized(geom_from_wkt('LineString(0 0, 10 0)'), 2, 3, 0.1, 0.2) → Randomly sized triangular waves with wavelengths between 2 and 3 and amplitudes between 0.1 and 0.2 along the linestring

../../../_images/triangular_wave_randomized.png

Symbolizing features with triangular randomized waves

13.2.13.130. union

Returns a geometry that represents the point set union of the geometries.

Sintaxă

union(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • geom_to_wkt( union( make_point(4, 4), make_point(5, 5) ) ) → «MULTIPOINT(4 4, 5 5)»

13.2.13.131. wave

Constructs rounded (sine-like) waves along the boundary of a geometry.

Sintaxă

wave(geometry, wavelength, amplitude, [strict=False])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • wavelength - wavelength of sine-like waveform

  • amplitude - amplitude of sine-like waveform

  • strict - By default the wavelength argument is treated as a „maximum wavelength”, where the actual wavelength will be dynamically adjusted so that an exact number of waves are created along the boundaries of the geometry. If the strict argument is set to true then the wavelength will be used exactly and an incomplete pattern may be used for the final waveform.

Exemple

  • wave(geom_from_wkt('LineString(0 0, 10 0)'), 3, 1) → Sine-like waves with wavelength 3 and amplitude 1 along the linestring

../../../_images/wave.png

Symbolizing features with waves

13.2.13.132. wave_randomized

Constructs randomized curved (sine-like) waves along the boundary of a geometry.

Sintaxă

wave_randomized(geometry, min_wavelength, max_wavelength, min_amplitude, max_amplitude, [seed=0])

[] marks optional arguments

Argumente

  • geometry - a geometry

  • min_wavelength - minimum wavelength of waves

  • max_wavelength - maximum wavelength of waves

  • min_amplitude - minimum amplitude of waves

  • max_amplitude - maximum amplitude of waves

  • seed - specifies a random seed for generating waves. If the seed is 0, then a completely random set of waves will be generated.

Exemple

  • wave_randomized(geom_from_wkt('LineString(0 0, 10 0)'), 2, 3, 0.1, 0.2) → Randomly sized curved waves with wavelengths between 2 and 3 and amplitudes between 0.1 and 0.2 along the linestring

../../../_images/wave_randomized.png

Symbolizing features with randomized waves

13.2.13.133. wedge_buffer

Returns a wedge shaped buffer originating from a point geometry.

Sintaxă

wedge_buffer(center, azimuth, width, outer_radius, [inner_radius=0.0])

[] marks optional arguments

Argumente

  • center - center point (origin) of buffer. Must be a point geometry.

  • azimuth - angle (in degrees) for the middle of the wedge to point.

  • width - buffer width (in degrees). Note that the wedge will extend to half of the angular width either side of the azimuth direction.

  • outer_radius - outer radius for buffers

  • inner_radius - optional inner radius for buffers

Exemple

  • wedge_buffer(center:=geom_from_wkt('POINT(1 2)'),azimuth:=90,width:=180,outer_radius:=1) → A wedge shaped buffer centered on the point (1,2), facing to the East, with a width of 180 degrees and outer radius of 1.

../../../_images/wedge_buffers.png

Wedge buffering features

Mai multe detalii: Algoritmul Create wedge buffers

13.2.13.134. within

Tests whether a geometry is within another. Returns TRUE if the geometry1 is completely within geometry2.

Sintaxă

within(geometry1, geometry2)

Argumente

  • geometry1 - a geometry

  • geometry2 - a geometry

Exemple

  • within( geom_from_wkt( 'POINT( 0.5 0.5)' ), geom_from_wkt( 'POLYGON((0 0, 0 1, 1 1, 1 0, 0 0))' ) ) → TRUE

  • within( geom_from_wkt( 'POINT( 5 5 )' ), geom_from_wkt( 'POLYGON((0 0, 0 1, 1 1, 1 0, 0 0 ))' ) ) → FALSE

Mai multe detalii: overlay_within

13.2.13.135. $x

Returns the x coordinate of the current point feature. If the feature is a multipoint feature, then the x-coordinate of the first point will be returned. WARNING: This function is deprecated. It is recommended to use the replacement x() function with @geometry variable instead.

Sintaxă

$x

Exemple

  • $x → 42

Further reading: x

13.2.13.136. x

Returns the x coordinate of a point geometry, or the x coordinate of the centroid for a non-point geometry.

Sintaxă

x(geometry)

Argumente

  • geometry - a geometry

Exemple

  • x( geom_from_wkt( 'POINT(2 5)' ) ) → 2

  • x( @geometry ) → x coordinate of the current feature’s centroid

13.2.13.137. $x_at

Retrieves a x coordinate of the current feature’s geometry. WARNING: This function is deprecated. It is recommended to use the replacement x_at function with @geometry variable instead.

Sintaxă

$x_at(vertex)

Argumente

  • vertex - index of the vertex of the current geometry (indices start at 0; negative values apply from the last index, starting at -1)

Exemple

  • $x_at(1) → 5

Further reading: x_at

13.2.13.138. x_at

Retrieves a x coordinate of the geometry.

Sintaxă

x_at(geometry, vertex)

Argumente

  • geometry - geometry object

  • vertex - index of the vertex of the geometry (indices start at 0; negative values apply from the last index, starting at -1)

Exemple

  • x_at( geom_from_wkt( 'POINT(4 5)' ), 0 ) → 4

13.2.13.139. x_max

Returns the maximum x coordinate of a geometry. Calculations are in the spatial reference system of this geometry.

Sintaxă

x_max(geometry)

Argumente

  • geometry - a geometry

Exemple

  • x_max( geom_from_wkt( 'LINESTRING(2 5, 3 6, 4 8)') ) → 4

13.2.13.140. x_min

Returns the minimum x coordinate of a geometry. Calculations are in the spatial reference system of this geometry.

Sintaxă

x_min(geometry)

Argumente

  • geometry - a geometry

Exemple

  • x_min( geom_from_wkt( 'LINESTRING(2 5, 3 6, 4 8)') ) → 2

13.2.13.141. $y

Returns the y coordinate of the current point feature. If the feature is a multipoint feature, then the y-coordinate of the first point will be returned. WARNING: This function is deprecated. It is recommended to use the replacement y() function with @geometry variable instead.

Sintaxă

$y

Exemple

  • $y → 42

Further reading: y

13.2.13.142. y

Returns the y coordinate of a point geometry, or the y coordinate of the centroid for a non-point geometry.

Sintaxă

y(geometry)

Argumente

  • geometry - a geometry

Exemple

  • y( geom_from_wkt( 'POINT(2 5)' ) ) → 5

  • y( @geometry ) → y coordinate of the current feature’s centroid

13.2.13.143. $y_at

Retrieves a y coordinate of the current feature’s geometry. WARNING: This function is deprecated. It is recommended to use the replacement y_at function with @geometry variable instead.

Sintaxă

$y_at(vertex)

Argumente

  • vertex - index of the vertex of the current geometry (indices start at 0; negative values apply from the last index, starting at -1)

Exemple

  • $y_at(1) → 2

Further reading: y_at

13.2.13.144. y_at

Retrieves a y coordinate of the geometry.

Sintaxă

y_at(geometry, vertex)

Argumente

  • geometry - geometry object

  • vertex - index of the vertex of the geometry (indices start at 0; negative values apply from the last index, starting at -1)

Exemple

  • y_at( geom_from_wkt( 'POINT(4 5)' ), 0 ) → 5

13.2.13.145. y_max

Returns the maximum y coordinate of a geometry. Calculations are in the spatial reference system of this geometry.

Sintaxă

y_max(geometry)

Argumente

  • geometry - a geometry

Exemple

  • y_max( geom_from_wkt( 'LINESTRING(2 5, 3 6, 4 8)') ) → 8

13.2.13.146. y_min

Returns the minimum y coordinate of a geometry. Calculations are in the spatial reference system of this geometry.

Sintaxă

y_min(geometry)

Argumente

  • geometry - a geometry

Exemple

  • y_min( geom_from_wkt( 'LINESTRING(2 5, 3 6, 4 8)') ) → 5

13.2.13.147. $z

Returns the z value of the current point feature if it is 3D. If the feature is a multipoint feature, then the z value of the first point will be returned. WARNING: This function is deprecated. It is recommended to use the replacement z() function with @geometry variable instead.

Sintaxă

$z

Exemple

  • $z → 123

13.2.13.148. z

Returns the z coordinate of a point geometry, or NULL if the geometry has no z value.

Sintaxă

z(geometry)

Argumente

  • geometry - a point geometry

Exemple

  • z( geom_from_wkt( 'POINTZ(2 5 7)' ) ) → 7

13.2.13.149. z_at

Retrieves a z coordinate of the geometry, or NULL if the geometry has no z value.

Sintaxă

z_at(geometry, vertex)

Argumente

  • geometry - geometry object

  • vertex - index of the vertex of the geometry (indices start at 0; negative values apply from the last index, starting at -1)

Exemple

  • z_at(geom_from_wkt('LineStringZ(0 0 0, 10 10 5, 10 10 0)'), 1) → 5

13.2.13.150. z_max

Returns the maximum z coordinate of a geometry, or NULL if the geometry has no z value.

Sintaxă

z_max(geometry)

Argumente

  • geometry - a geometry with z coordinate

Exemple

  • z_max( geom_from_wkt( 'POINT ( 0 0 1 )' ) ) → 1

  • z_max( geom_from_wkt( 'MULTIPOINT ( 0 0 1 , 1 1 3 )' ) ) → 3

  • z_max( make_line( make_point( 0,0,0 ), make_point( -1,-1,-2 ) ) ) → 0

  • z_max( geom_from_wkt( 'LINESTRING( 0 0 0, 1 0 2, 1 1 -1 )' ) ) → 2

  • z_max( geom_from_wkt( 'POINT ( 0 0 )' ) ) → NULL

13.2.13.151. z_min

Returns the minimum z coordinate of a geometry, or NULL if the geometry has no z value.

Sintaxă

z_min(geometry)

Argumente

  • geometry - a geometry with z coordinate

Exemple

  • z_min( geom_from_wkt( 'POINT ( 0 0 1 )' ) ) → 1

  • z_min( geom_from_wkt( 'MULTIPOINT ( 0 0 1 , 1 1 3 )' ) ) → 1

  • z_min( make_line( make_point( 0,0,0 ), make_point( -1,-1,-2 ) ) ) → -2

  • z_min( geom_from_wkt( 'LINESTRING( 0 0 0, 1 0 2, 1 1 -1 )' ) ) → -1

  • z_min( geom_from_wkt( 'POINT ( 0 0 )' ) ) → NULL

13.2.14. Layout Functions

This group contains functions to manipulate print layout items properties.

13.2.14.1. item_variables

Returns a map of variables from a layout item inside this print layout.

Sintaxă

item_variables(id)

Argumente

  • id - layout item ID

Exemple

  • map_get( item_variables('Map 0'), 'map_scale') → scale of the item «Map 0» in the current print layout

Mai multe detalii: Lista variabilelor implicite :ref:` <expression_variables>`

13.2.14.2. map_credits

Returns a list of credit (usage rights) strings for the layers shown in a layout, or specific layout map item.

Sintaxă

map_credits([id], [include_layer_names=false], [layer_name_separator=»: «])

[] marks optional arguments

Argumente

  • id - Map item ID. If not specified, the layers from all maps in the layout will be used.

  • include_layer_names - Set to true to include layer names before their credit strings

  • layer_name_separator - String to insert between layer names and their credit strings, if include_layer_names is true

Exemple

  • array_to_string( map_credits() ) → comma separated list of layer credits for all layers shown in all map items in the layout, e.g «CC-BY-NC, CC-BY-SA»

  • array_to_string( map_credits( 'Main Map' ) ) → comma separated list of layer credits for layers shown in the «Main Map» layout item, e.g «CC-BY-NC, CC-BY-SA»

  • array_to_string( map_credits( 'Main Map', include_layer_names := true, layer_name_separator := ': ' ) ) → comma separated list of layer names and their credits for layers shown in the «Main Map» layout item, e.g. «Railway lines: CC-BY-NC, Basemap: CC-BY-SA»

This function requires the Access metadata properties of the layers to have been filled.

13.2.15. Map Layers

This group contains a list of the available layers in the current project and, for each layer, their fields (stored in the dataset, virtual or auxiliary ones as well as from joins). The fields can be interacted the same way as mentioned in Fields and Values, except that a double-click will add the name as a string (single quoted) to the expression instead of as a field reference given that they do not belong to the active layer. This offers a convenient way to write expressions referring to different layers, such as when performing aggregates, attribute or spatial queries.

It also provides some convenient functions to manipulate layers.

13.2.15.1. decode_uri

Takes a layer and decodes the uri of the underlying data provider. It depends on the dataprovider, which data is available.

Sintaxă

decode_uri(layer, [part])

[] marks optional arguments

Argumente

  • layer - The layer for which the uri should be decoded.

  • part - The part of the uri to return. If unspecified, a map with all uri parts will be returned.

Exemple

  • decode_uri(@layer) → {«layerId»: «0», «layerName»: «», «path»: «/home/qgis/shapefile.shp»}

  • decode_uri(@layer) → {«layerId»: NULL, «layerName»: «layer», «path»: «/home/qgis/geopackage.gpkg»}

  • decode_uri(@layer, 'path') → «C:\my_data\qgis\shape.shp»

13.2.15.2. layer_property

Returns a matching layer property or metadata value.

Sintaxă

layer_property(layer, property)

Argumente

  • layer - a string, representing either a layer name or layer ID

  • property - a string corresponding to the property to return. Valid options are:

    • name: layer name

    • id: layer ID

    • title: metadata title string

    • abstract: metadata abstract string

    • keywords: metadata keywords

    • data_url: metadata URL

    • attribution: metadata attribution string

    • attribution_url: metadata attribution URL

    • source: layer source

    • min_scale: minimum display scale for layer

    • max_scale: maximum display scale for layer

    • is_editable: if layer is in edit mode

    • crs: layer CRS

    • crs_definition: layer CRS full definition

    • crs_description: layer CRS description

    • crs_ellipsoid: acronym of the layer CRS ellipsoid

    • extent: layer extent (as a geometry object)

    • distance_units: layer distance units

    • type: layer type, e.g., Vector or Raster

    • storage_type: storage format (vector layers only)

    • geometry_type: geometry type, e.g., Point (vector layers only)

    • feature_count: approximate feature count for layer (vector layers only)

    • path: File path to the layer data source. Only available for file based layers.

Exemple

  • layer_property('streets','title') → «Basemap Streets»

  • layer_property('airports','feature_count') → 120

  • layer_property('landsat','crs') → «EPSG:4326»

Mai multe detalii: vector, raster and mesh layer properties

13.2.15.3. load_layer

Loads a layer by source URI and provider name.

Sintaxă

load_layer(uri, provider)

Argumente

  • uri - layer source URI string

  • provider - layer data provider name

Exemple

  • layer_property(load_layer('c:/data/roads.shp', 'ogr'), 'feature_count') → count of features from the c:/data/roads.shp vector layer

13.2.16. Maps Functions

This group contains functions to create or manipulate keys and values of map data structures (also known as dictionary objects, key-value pairs, or associative arrays). Unlike the list data structure where values order matters, the order of the key-value pairs in the map object is not relevant and values are identified by their keys.

13.2.16.1. from_json

Încarcă un șir formatat JSON.

Sintaxă

from_json(string)

Argumente

  • string - șir JSON

Exemple

  • from_json('{"qgis":"rocks"}') → { «qgis»: «rocks» }

  • from_json('[1,2,3]') → [1,2,3]

13.2.16.2. hstore_to_map

Creează o hartă dintr-un șir formatat în hstore.

Sintaxă

hstore_to_map(string)

Argumente

  • string - șirul de intrare

Exemple

  • hstore_to_map('qgis=>rocks') → { «qgis»: «rocks» }

13.2.16.3. map

Returnează o hartă care conține toate cheile și valorile transmise ca pereche de parametri.

Sintaxă

map(key1, value1, key2, value2, …)

Argumente

  • key - o cheie (șir)

  • value - o valoare

Exemple

  • map('1','one','2', 'two') → { «1»: «one», «2»: «two» }

  • map('1','one','2', 'two')['1'] → «one»

13.2.16.4. map_akeys

Returnează toate cheile unei hărți într-un tablou.

Sintaxă

map_akeys(map)

Argumente

  • map - o hartă

Exemple

  • map_akeys(map('1','one','2','two')) → [ «1», «2» ]

13.2.16.5. map_avals

Returnează toate valorile unei hărți într-o matrice.

Sintaxă

map_avals(map)

Argumente

  • map - o hartă

Exemple

  • map_avals(map('1','one','2','two')) → [ «one», «two» ]

13.2.16.6. map_concat

Returnează o hartă care conține toate intrările hărților date. Dacă două hărți conțin aceeași cheie, se ia valoarea celei de-a doua hărți.

Sintaxă

map_concat(map1, map2, …)

Argumente

  • map - o hartă

Exemple

  • map_concat(map('1','one', '2','overridden'),map('2','two', '3','three')) → { «1»: «one», «2»: «two», «3»: «three» }

13.2.16.7. map_delete

Returnează o hartă cu cheia dată și valoarea ștearsă corespunzătoare ei.

Sintaxă

map_delete(map, key)

Argumente

  • map - o hartă

  • key - cheia de șters

Exemple

  • map_delete(map('1','one','2','two'),'2') → { «1»: «one» }

13.2.16.8. map_exist

Returns TRUE if the given key exists in the map.

Sintaxă

map_exist(map, key)

Argumente

  • map - o hartă

  • key - cheia de căutare

Exemple

  • map_exist(map('1','one','2','two'),'3') → FALSE

13.2.16.9. map_get

Returnează valoarea unei hărți, având în vedere cheia acesteia. Returnează NULL atunci când cheia nu există.

Sintaxă

map_get(map, key)

Argumente

  • map - o hartă

  • key - cheia de căutare

Exemple

  • map_get(map('1','one','2','two'),'2') → «two»

  • map_get( item_variables('Map 0'), 'map_scale') → scara elementului «Map 0» (dacă există) în compoziția curentă

Sugestie

You can also use the index operator ([]) to get a value from a map.

13.2.16.10. map_insert

Returnează o hartă cu o cheie/o valoare adăugată. Atunci când cheia există deja, valoarea acesteia este suprascrisă.

Sintaxă

map_insert(map, key, value)

Argumente

  • map - o hartă

  • key - cheia de adăugat

  • value - valoarea de adăugat

Exemple

  • map_insert(map('1','one'),'3','three') → { «1»: «one», «3»: «three» }

  • map_insert(map('1','one','2','overridden'),'2','two') → { «1»: «one», «2»: «two» }

13.2.16.11. map_prefix_keys

Returns a map with all keys prefixed by a given string.

Sintaxă

map_prefix_keys(map, prefix)

Argumente

  • map - o hartă

  • prefix - a string

Exemple

  • map_prefix_keys(map('1','one','2','two'), 'prefix-') → { «prefix-1»: «one», «prefix-2»: «two» }

13.2.16.12. map_to_hstore

Îmbină elementele hărții într-un șir formatat hstore.

Sintaxă

map_to_hstore(map)

Argumente

  • map - harta de intrare

Exemple

  • map_to_hstore(map('qgis','rocks')) → «„qgis”=>”rocks”»

13.2.16.13. map_to_html_dl

Merge map elements into a HTML definition list string.

Sintaxă

map_to_html_dl(map)

Argumente

  • map - harta de intrare

Exemple

  • map_to_html_dl(map('qgis','rocks')) → <dl><dt>qgis</dt><dd>rocks</dd></dl>

13.2.16.14. map_to_html_table

Merge map elements into a HTML table string.

Sintaxă

map_to_html_table(map)

Argumente

  • map - harta de intrare

Exemple

  • map_to_html_table(map('qgis','rocks')) → <table><thead><th>qgis</th></thead><tbody><tr><td>rocks</td></tr></tbody></table>

13.2.16.15. to_json

Creează un șir formatat JSON dintr-o hartă, matrice sau altă valoare.

Sintaxă

to_json(value)

Argumente

  • value - valoarea de intrare

Exemple

  • to_json(map('qgis','rocks')) → {„qgis”:”rocks”}

  • to_json(array(1,2,3)) → [1,2,3]

13.2.16.16. url_encode

Returns an URL encoded string from a map. Transforms all characters in their properly-encoded form producing a fully-compliant query string.

Note that the plus sign «+» is not converted.

Sintaxă

url_encode(map)

Argumente

  • map - a map.

Exemple

  • url_encode(map('a&+b', 'a and plus b', 'a=b', 'a equals b')) → «a%26+b=a%20and%20plus%20b&a%3Db=a%20equals%20b»

13.2.17. Funcțiile Matematice

Acest grup conține funcții matematice (ex.: rădăcina pătrată, sin și cos).

13.2.17.1. abs

Returns the absolute value of a number.

Sintaxă

abs(value)

Argumente

  • value - a number

Exemple

  • abs(-2) → 2

13.2.17.2. acos

Returns the inverse cosine of a value in radians.

Sintaxă

acos(value)

Argumente

  • value - cosine of an angle in radians

Exemple

  • acos(0.5) → 1.0471975511966

13.2.17.3. asin

Returns the inverse sine of a value in radians.

Sintaxă

asin(value)

Argumente

  • value - sine of an angle in radians

Exemple

  • asin(1.0) → 1.5707963267949

13.2.17.4. atan

Returns the inverse tangent of a value in radians.

Sintaxă

atan(value)

Argumente

  • value - tan of an angle in radians

Exemple

  • atan(0.5) → 0.463647609000806

13.2.17.5. atan2

Returns the inverse tangent of dy/dx by using the signs of the two arguments to determine the quadrant of the result.

Sintaxă

atan2(dy, dx)

Argumente

  • dy - y coordinate difference

  • dx - x coordinate difference

Exemple

  • atan2(1.0, 1.732) → 0.523611477769969

13.2.17.6. ceil

Rounds a number upwards.

Sintaxă

ceil(value)

Argumente

  • value - a number

Exemple

  • ceil(4.9) → 5

  • ceil(-4.9) → -4

13.2.17.7. clamp

Restricts an input value to a specified range.

Sintaxă

clamp(minimum, input, maximum)

Argumente

  • minimum - the smallest value input is allowed to take.

  • input - a value which will be restricted to the range specified by minimum and maximum

  • maximum - the largest value input is allowed to take

Exemple

  • clamp(1,5,10) → 5

    input is between 1 and 10 so is returned unchanged

  • clamp(1,0,10) → 1

    input is less than minimum value of 1, so function returns 1

  • clamp(1,11,10) → 10

    input is greater than maximum value of 10, so function returns 10

13.2.17.8. cos

Returns cosine of an angle.

Sintaxă

cos(angle)

Argumente

  • angle - angle in radians

Exemple

  • cos(1.571) → 0.000796326710733263

13.2.17.9. degrees

Converts from radians to degrees.

Sintaxă

degrees(radians)

Argumente

  • radians - numeric value

Exemple

  • degrees(3.14159) → 180

  • degrees(1) → 57.2958

13.2.17.10. exp

Returns exponential of an value.

Sintaxă

exp(value)

Argumente

  • value - number to return exponent of

Exemple

  • exp(1.0) → 2.71828182845905

13.2.17.11. floor

Rounds a number downwards.

Sintaxă

floor(value)

Argumente

  • value - a number

Exemple

  • floor(4.9) → 4

  • floor(-4.9) → -5

13.2.17.12. ln

Returns the natural logarithm of a value.

Sintaxă

ln(value)

Argumente

  • value - numeric value

Exemple

  • ln(1) → 0

  • ln(2.7182818284590452354) → 1

13.2.17.13. log

Returns the value of the logarithm of the passed value and base.

Sintaxă

log(base, value)

Argumente

  • base - any positive number

  • value - any positive number

Exemple

  • log(2, 32) → 5

  • log(0.5, 32) → -5

13.2.17.14. log10

Returns the value of the base 10 logarithm of the passed expression.

Sintaxă

log10(value)

Argumente

  • value - any positive number

Exemple

  • log10(1) → 0

  • log10(100) → 2

13.2.17.15. max

Returns the largest value in a set of values.

Sintaxă

max(value1, value2, …)

Argumente

  • value - a number

Exemple

  • max(2,10.2,5.5) → 10.2

  • max(20.5,NULL,6.2) → 20.5

13.2.17.16. min

Returns the smallest value in a set of values.

Sintaxă

min(value1, value2, …)

Argumente

  • value - a number

Exemple

  • min(20.5,10,6.2) → 6.2

  • min(2,-10.3,NULL) → -10.3

13.2.17.17. pi

Returns value of pi for calculations.

Sintaxă

pi()

Exemple

  • pi() → 3.14159265358979

13.2.17.18. radians

Converts from degrees to radians.

Sintaxă

radians(degrees)

Argumente

  • degrees - numeric value

Exemple

  • radians(180) → 3.14159

  • radians(57.2958) → 1

13.2.17.19. rand

Returns a random integer within the range specified by the minimum and maximum argument (inclusive). If a seed is provided, the returned will always be the same, depending on the seed.

Sintaxă

rand(min, max, [seed=NULL])

[] marks optional arguments

Argumente

  • min - an integer representing the smallest possible random number desired

  • max - an integer representing the largest possible random number desired

  • seed - any value to use as seed

Exemple

  • rand(1, 10) → 8

13.2.17.20. randf

Returns a random float within the range specified by the minimum and maximum argument (inclusive). If a seed is provided, the returned will always be the same, depending on the seed.

Sintaxă

randf([min=0.0], [max=1.0], [seed=NULL])

[] marks optional arguments

Argumente

  • min - an float representing the smallest possible random number desired

  • max - an float representing the largest possible random number desired

  • seed - any value to use as seed

Exemple

  • randf(1, 10) → 4.59258286403147

13.2.17.21. round

Rounds a number to number of decimal places.

Sintaxă

round(value, [places=0])

[] marks optional arguments

Argumente

  • value - decimal number to be rounded

  • places - Optional integer representing number of places to round decimals to. Can be negative.

Exemple

  • round(1234.567, 2) → 1234.57

  • round(1234.567) → 1235

  • round(1234.567, -1) → 1230

13.2.17.22. scale_exponential

Transforms a given value from an input domain to an output range using an exponential curve. This function can be used to ease values in or out of the specified output range.

Sintaxă

scale_exponential(value, domain_min, domain_max, range_min, range_max, exponent)

Argumente

  • value - A value in the input domain. The function will return a corresponding scaled value in the output range.

  • domain_min - Specifies the minimum value in the input domain, the smallest value the input value should take.

  • domain_max - Specifies the maximum value in the input domain, the largest value the input value should take.

  • range_min - Specifies the minimum value in the output range, the smallest value which should be output by the function.

  • range_max - Specifies the maximum value in the output range, the largest value which should be output by the function.

  • exponent - A positive value (greater than 0), which dictates the way input values are mapped to the output range. Large exponents will cause the output values to «ease in», starting slowly before accelerating as the input values approach the domain maximum. Smaller exponents (less than 1) will cause output values to «ease out», where the mapping starts quickly but slows as it approaches the domain maximum.

Exemple

  • scale_exp(5,0,10,0,100,2) → 25

    easing in, using an exponent of 2

  • scale_exp(3,0,10,0,100,0.5) → 54.772

    easing out, using an exponent of 0.5

13.2.17.23. scale_linear

Transforms a given value from an input domain to an output range using linear interpolation.

Sintaxă

scale_linear(value, domain_min, domain_max, range_min, range_max)

Argumente

  • value - A value in the input domain. The function will return a corresponding scaled value in the output range.

  • domain_min - Specifies the minimum value in the input domain, the smallest value the input value should take.

  • domain_max - Specifies the maximum value in the input domain, the largest value the input value should take.

  • range_min - Specifies the minimum value in the output range, the smallest value which should be output by the function.

  • range_max - Specifies the maximum value in the output range, the largest value which should be output by the function.

Exemple

  • scale_linear(5,0,10,0,100) → 50

  • scale_linear(0.2,0,1,0,360) → 72

    scaling a value between 0 and 1 to an angle between 0 and 360

  • scale_linear(1500,1000,10000,9,20) → 9.6111111

    scaling a population which varies between 1000 and 10000 to a font size between 9 and 20

13.2.17.24. scale_polynomial

Transforms a given value from an input domain to an output range using a polynomial curve. This function can be used to ease values in or out of the specified output range.

Sintaxă

scale_polynomial(value, domain_min, domain_max, range_min, range_max, exponent)

Argumente

  • value - A value in the input domain. The function will return a corresponding scaled value in the output range.

  • domain_min - Specifies the minimum value in the input domain, the smallest value the input value should take.

  • domain_max - Specifies the maximum value in the input domain, the largest value the input value should take.

  • range_min - Specifies the minimum value in the output range, the smallest value which should be output by the function.

  • range_max - Specifies the maximum value in the output range, the largest value which should be output by the function.

  • exponent - A positive value (greater than 0), which dictates the way input values are mapped to the output range. Large exponents will cause the output values to «ease in», starting slowly before accelerating as the input values approach the domain maximum. Smaller exponents (less than 1) will cause output values to «ease out», where the mapping starts quickly but slows as it approaches the domain maximum.

Exemple

  • scale_polynomial(5,0,10,0,100,2) → 25

    easing in, using an exponent of 2

  • scale_polynomial(3,0,10,0,100,0.5) → 54.772

    easing out, using an exponent of 0.5

13.2.17.25. sin

Returns the sine of an angle.

Sintaxă

sin(angle)

Argumente

  • angle - angle in radians

Exemple

  • sin(1.571) → 0.999999682931835

13.2.17.26. sqrt

Returns square root of a value.

Sintaxă

sqrt(value)

Argumente

  • value - a number

Exemple

  • sqrt(9) → 3

13.2.17.27. tan

Returns the tangent of an angle.

Sintaxă

tan(angle)

Argumente

  • angle - angle in radians

Exemple

  • tan(1.0) → 1.5574077246549

13.2.18. Meshes Functions

This group contains functions which calculate or return mesh related values.

13.2.18.1. $face_area

Returns the area of the current mesh face. The area calculated by this function respects both the current project’s ellipsoid setting and area unit settings. For example, if an ellipsoid has been set for the project then the calculated area will be ellipsoidal, and if no ellipsoid is set then the calculated area will be planimetric.

Sintaxă

$face_area

Exemple

  • $face_area → 42

13.2.18.2. $face_index

Returns the index of the current mesh face.

Sintaxă

$face_index

Exemple

  • $face_index → 4581

13.2.18.3. $vertex_as_point

Returns the current vertex as a point geometry.

Sintaxă

$vertex_as_point

Exemple

  • geom_to_wkt( $vertex_as_point ) → «POINT(800 1500 41)»

13.2.18.4. $vertex_index

Returns the index of the current mesh vertex.

Sintaxă

$vertex_index

Exemple

  • $vertex_index → 9874

13.2.18.5. $vertex_x

Returns the X coordinate of the current mesh vertex.

Sintaxă

$vertex_x

Exemple

  • $vertex_x → 42.12

13.2.18.6. $vertex_y

Returns the Y coordinate of the current mesh vertex.

Sintaxă

$vertex_y

Exemple

  • $vertex_y → 12.24

13.2.18.7. $vertex_z

Returns the Z value of the current mesh vertex.

Sintaxă

$vertex_z

Exemple

  • $vertex_z → 42

13.2.19. Operatori

Acest grup cuprinde operatorii (ex.: +, -, *). De notat că pentru majoritatea funcțiilor matematice de mai jos, în cazul în care una dintre intrări are valoarea NULL, atunci rezultatul este NULL.

13.2.19.1. %

Remainder of division. Takes the sign of the dividend.

Sintaxă

a % b

Argumente

  • a - value

  • b - value

Exemple

  • 9 % 2 → 1

  • 9 % -2 → 1

  • -9 % 2 → -1

  • 5 % NULL → NULL

13.2.19.2. *

Multiplication of two values

Sintaxă

a * b

Argumente

  • a - value

  • b - value

Exemple

  • 5 * 4 → 20

  • 5 * NULL → NULL

13.2.19.3. +

Addition of two values. If one of the values is NULL the result will be NULL.

Sintaxă

a + b

Argumente

  • a - value

  • b - value

Exemple

  • 5 + 4 → 9

  • 5 + NULL → NULL

  • 'QGIS ' + 'ROCKS' → «QGIS ROCKS»

  • to_datetime('2020-08-01 12:00:00') + '1 day 2 hours' → 2020-08-02T14:00:00

Mai multe detalii: concat, ||

13.2.19.4. -

Subtraction of two values. If one of the values is NULL the result will be NULL.

Sintaxă

a - b

Argumente

  • a - value

  • b - value

Exemple

  • 5 - 4 → 1

  • 5 - NULL → NULL

  • to_datetime('2012-05-05 12:00:00') - to_interval('1 day 2 hours') → 2012-05-04T10:00:00

13.2.19.5. /

Division of two values

Sintaxă

a / b

Argumente

  • a - value

  • b - value

Exemple

  • 5 / 4 → 1.25

  • 5 / NULL → NULL

13.2.19.6. //

Floor division of two values

Sintaxă

a // b

Argumente

  • a - value

  • b - value

Exemple

  • 9 // 2 → 4

13.2.19.7. <

Compares two values and evaluates to 1 if the left value is less than the right value.

Sintaxă

a < b

Argumente

  • a - value

  • b - value

Exemple

  • 5 < 4 → FALSE

  • 5 < 5 → FALSE

  • 4 < 5 → TRUE

13.2.19.8. <=

Compares two values and evaluates to 1 if the left value is less or equal than the right value.

Sintaxă

a <= b

Argumente

  • a - value

  • b - value

Exemple

  • 5 <= 4 → FALSE

  • 5 <= 5 → TRUE

  • 4 <= 5 → TRUE

13.2.19.9. <>

Compares two values and evaluates to 1 if they are not equal.

Sintaxă

a <> b

Argumente

  • a - value

  • b - value

Exemple

  • 5 <> 4 → TRUE

  • 4 <> 4 → FALSE

  • 5 <> NULL → NULL

  • NULL <> NULL → NULL

13.2.19.10. =

Compares two values and evaluates to 1 if they are equal.

Sintaxă

a = b

Argumente

  • a - value

  • b - value

Exemple

  • 5 = 4 → FALSE

  • 4 = 4 → TRUE

  • 5 = NULL → NULL

  • NULL = NULL → NULL

13.2.19.11. >

Compares two values and evaluates to 1 if the left value is greater than the right value.

Sintaxă

a > b

Argumente

  • a - value

  • b - value

Exemple

  • 5 > 4 → TRUE

  • 5 > 5 → FALSE

  • 4 > 5 → FALSE

13.2.19.12. >=

Compares two values and evaluates to 1 if the left value is greater or equal than the right value.

Sintaxă

a >= b

Argumente

  • a - value

  • b - value

Exemple

  • 5 >= 4 → TRUE

  • 5 >= 5 → TRUE

  • 4 >= 5 → FALSE

13.2.19.13. AND

Returns TRUE when conditions a and b are true.

Sintaxă

a AND b

Argumente

  • a - condition

  • b - condition

Exemple

  • TRUE AND TRUE → TRUE

  • TRUE AND FALSE → FALSE

  • 4 = 2+2 AND 1 = 1 → TRUE

  • 4 = 2+2 AND 1 = 2 → FALSE

13.2.19.14. BETWEEN

Returns TRUE if value is within the specified range. The range is considered inclusive of the bounds. To test for exclusion NOT BETWEEN can be used.

Sintaxă

value BETWEEN lower_bound AND higher_bound

Argumente

  • value - the value to compare with a range. It can be a string, a number or a date.

  • lower_bound AND higher_bound - range bounds

Exemple

  • 'B' BETWEEN 'A' AND 'C' → TRUE

  • 2 BETWEEN 1 AND 3 → TRUE

  • 2 BETWEEN 2 AND 3 → TRUE

  • 'B' BETWEEN 'a' AND 'c' → FALSE

  • lower('B') BETWEEN 'a' AND 'b' → TRUE

Notă

value BETWEEN lower_bound AND higher_bound is the same as „value >= lower_bound AND value <= higher_bound”.

Mai multe detalii: NOT BETWEEN

13.2.19.15. ILIKE

Returns TRUE if the first parameter matches case-insensitive the supplied pattern. LIKE can be used instead of ILIKE to make the match case-sensitive. Works with numbers also.

Sintaxă

string/number ILIKE pattern

Argumente

  • string/number - string to search

  • pattern - pattern to find, you can use «%» as a wildcard, «_» as a single char and «\\» to escape these special characters.

Exemple

  • 'A' ILIKE 'A' → TRUE

  • 'A' ILIKE 'a' → TRUE

  • 'A' ILIKE 'B' → FALSE

  • 'ABC' ILIKE 'b' → FALSE

  • 'ABC' ILIKE 'B' → FALSE

  • 'ABC' ILIKE '_b_' → TRUE

  • 'ABC' ILIKE '_B_' → TRUE

  • 'ABCD' ILIKE '_b_' → FALSE

  • 'ABCD' ILIKE '_B_' → FALSE

  • 'ABCD' ILIKE '_b%' → TRUE

  • 'ABCD' ILIKE '_B%' → TRUE

  • 'ABCD' ILIKE '%b%' → TRUE

  • 'ABCD' ILIKE '%B%' → TRUE

  • 'ABCD%' ILIKE 'abcd\\%' → TRUE

  • 'ABCD' ILIKE '%B\\%' → FALSE

13.2.19.16. IN

Returns TRUE if value is found within a list of values.

Sintaxă

a IN b

Argumente

  • a - value

  • b - list of values

Exemple

  • 'A' IN ('A','B') → TRUE

  • 'A' IN ('C','B') → FALSE

13.2.19.17. IS

Returns TRUE if a is the same as b.

Sintaxă

a IS b

Argumente

  • a - any value

  • b - any value

Exemple

  • 'A' IS 'A' → TRUE

  • 'A' IS 'a' → FALSE

  • 4 IS 4 → TRUE

  • 4 IS 2+2 → TRUE

  • 4 IS 2 → FALSE

  • @geometry IS NULL → 0, if your geometry is not NULL

13.2.19.18. IS NOT

Returns TRUE if a is not the same as b.

Sintaxă

a IS NOT b

Argumente

  • a - value

  • b - value

Exemple

  • 'a' IS NOT 'b' → TRUE

  • 'a' IS NOT 'a' → FALSE

  • 4 IS NOT 2+2 → FALSE

13.2.19.19. LIKE

Returns TRUE if the first parameter matches the supplied pattern. Works with numbers also.

Sintaxă

string/number LIKE pattern

Argumente

  • string/number - value

  • pattern - pattern to compare value with, you can use «%» as a wildcard, «_» as a single char and «\\» to escape these special characters.

Exemple

  • 'A' LIKE 'A' → TRUE

  • 'A' LIKE 'a' → FALSE

  • 'A' LIKE 'B' → FALSE

  • 'ABC' LIKE 'B' → FALSE

  • 'ABC' LIKE '_B_' → TRUE

  • 'ABCD' LIKE '_B_' → FALSE

  • 'ABCD' LIKE '_B%' → TRUE

  • 'ABCD' LIKE '%B%' → TRUE

  • '1%' LIKE '1\\%' → TRUE

  • '1_' LIKE '1\\%' → FALSE

13.2.19.20. NOT

Negates a condition.

Sintaxă

NOT a

Argumente

  • a - condition

Exemple

  • NOT 1 → FALSE

  • NOT 0 → TRUE

13.2.19.21. NOT BETWEEN

Returns TRUE if value is not within the specified range. The range is considered inclusive of the bounds.

Sintaxă

value NOT BETWEEN lower_bound AND higher_bound

Argumente

  • value - the value to compare with a range. It can be a string, a number or a date.

  • lower_bound AND higher_bound - range bounds

Exemple

  • 'B' NOT BETWEEN 'A' AND 'C' → FALSE

  • 1.0 NOT BETWEEN 1.1 AND 1.2 → TRUE

  • 2 NOT BETWEEN 2 AND 3 → FALSE

  • 'B' NOT BETWEEN 'a' AND 'c' → TRUE

  • lower('B') NOT BETWEEN 'a' AND 'b' → FALSE

Notă

value NOT BETWEEN lower_bound AND higher_bound is the same as „value < lower_bound OR value > higher_bound”.

Mai multe detalii: BETWEEN

13.2.19.22. OR

Returns TRUE when condition a or b is true.

Sintaxă

a OR b

Argumente

  • a - condition

  • b - condition

Exemple

  • 4 = 2+2 OR 1 = 1 → TRUE

  • 4 = 2+2 OR 1 = 2 → TRUE

  • 4 = 2   OR 1 = 2 → FALSE

13.2.19.23. []

Index operator. Returns an element from an array or map value.

Sintaxă

[index]

Argumente

  • index - array index or map key value

Exemple

  • array(1,2,3)[0] → 1

  • array(1,2,3)[2] → 3

  • array(1,2,3)[-1] → 3

  • map('a',1,'b',2)['a'] → 1

  • map('a',1,'b',2)['b'] → 2

Mai multe detalii: array_get, map_get

13.2.19.24. ^

Power of two values.

Sintaxă

a ^ b

Argumente

  • a - value

  • b - value

Exemple

  • 5 ^ 4 → 625

  • 5 ^ NULL → NULL

13.2.19.25. ||

Joins two values together into a string.

If one of the values is NULL the result will be NULL. See the CONCAT function for a different behavior.

Sintaxă

a || b

Argumente

  • a - value

  • b - value

Exemple

  • 'Here' || ' and ' || 'there' → «Here and there»

  • 'Nothing' || NULL → NULL

  • 'Dia: ' || "Diameter" → «Dia: 25»

  • 1 || 2 → «12»

Mai multe detalii: concat, +

13.2.19.26. ~

Performs a regular expression match on a string value. Backslash characters must be double escaped (e.g., „\\s” to match a white space character).

Sintaxă

string ~ regex

Argumente

  • string - A string value

  • regex - A regular expression. Slashes must be escaped, eg \\d.

Exemple

  • 'hello' ~ 'll' → TRUE

  • 'hello' ~ '^ll' → FALSE

  • 'hello' ~ 'llo$' → TRUE

  • 'abc123' ~ '\\d+' → TRUE

Mai multe detalii: regexp_match

13.2.20. Processing Functions

This group contains functions that operate on processing algorithms.

13.2.20.1. parameter

Returns the value of a processing algorithm input parameter.

Sintaxă

parameter(name)

Argumente

  • name - name of the corresponding input parameter

Exemple

  • parameter('BUFFER_SIZE') → 5.6

13.2.21. Rasters Functions

This group contains functions to operate on raster layer.

13.2.21.1. raster_attributes

Returns a map with the fields names as keys and the raster attribute table values as values from the attribute table entry that matches the given raster value.

Sintaxă

raster_attributes(layer, band, value)

Argumente

  • layer - the name or id of a raster layer

  • band - the band number for the associated attribute table lookup.

  • value - raster value

Exemple

  • raster_attributes('vegetation', 1, raster_value('vegetation', 1, make_point(1,1))) → {«class»: «Vegetated», «subclass»: «Trees»}

13.2.21.2. raster_statistic

Returns statistics from a raster layer.

Sintaxă

raster_statistic(layer, band, property)

Argumente

  • layer - a string, representing either a raster layer name or layer ID

  • band - integer representing the band number from the raster layer, starting at 1

  • property - a string corresponding to the property to return. Valid options are:

    • min: minimum value

    • max: maximum value

    • avg: average (mean) value

    • stdev: standard deviation of values

    • range: range of values (max - min)

    • sum: sum of all values from raster

Exemple

  • raster_statistic('lc',1,'avg') → Average value from band 1 from «lc» raster layer

  • raster_statistic('ac2010',3,'min') → Minimum value from band 3 from «ac2010» raster layer

13.2.21.3. raster_value

Returns the raster value found at the provided point.

Sintaxă

raster_value(layer, band, point)

Argumente

  • layer - the name or id of a raster layer

  • band - the band number to sample the value from.

  • point - point geometry (for multipart geometries having more than one part, a NULL value will be returned)

Exemple

  • raster_value('dem', 1, make_point(1,1)) → 25

13.2.22. Record and Attributes Functions

Acest grup conține funcții care operează asupra identificatorilor de înregistrare.

13.2.22.1. atribut

Returns an attribute from a feature.

Variant 1

Returns the value of an attribute from the current feature.

Sintaxă

attribute(attribute_name)

Argumente

  • attribute_name - name of attribute to be returned

Exemple

  • attribute( 'name' ) → value stored in «name» attribute for the current feature

Variant 2

Allows the target feature and attribute name to be specified.

Sintaxă

attribute(feature, attribute_name)

Argumente

  • feature - a feature

  • attribute_name - name of attribute to be returned

Exemple

  • attribute( @atlas_feature, 'name' ) → value stored in «name» attribute for the current atlas feature

13.2.22.2. attributes

Returns a map containing all attributes from a feature, with field names as map keys.

Variant 1

Returns a map of all attributes from the current feature.

Sintaxă

attributes()

Exemple

  • attributes()['name'] → value stored in «name» attribute for the current feature

Variant 2

Allows the target feature to be specified.

Sintaxă

attributes(feature)

Argumente

  • feature - a feature

Exemple

  • attributes( @atlas_feature )['name'] → value stored in «name» attribute for the current atlas feature

Mai multe detalii: Maps Functions

13.2.22.3. $currentfeature

Returns the current feature being evaluated. This can be used with the «attribute» function to evaluate attribute values from the current feature. WARNING: This function is deprecated. It is recommended to use the replacement @feature variable instead.

Sintaxă

$currentfeature

Exemple

  • attribute( $currentfeature, 'name' ) → value stored in «name» attribute for the current feature

13.2.22.4. display_expression

Returns the display expression for a given feature in a layer. The expression is evaluated by default. Can be used with zero, one or more arguments, see below for details.

No parameters

If called with no parameters, the function will evaluate the display expression of the current feature in the current layer.

Sintaxă

display_expression()

Exemple

  • display_expression() → The display expression of the current feature in the current layer.

One «feature» parameter

If called with a «feature» parameter only, the function will evaluate the specified feature from the current layer.

Sintaxă

display_expression(feature)

Argumente

  • feature - The feature which should be evaluated.

Exemple

  • display_expression(@atlas_feature) → The display expression of the current atlas feature.

Layer and feature parameters

If the function is called with both a layer and a feature, it will evaluate the specified feature from the specified layer.

Sintaxă

display_expression(layer, feature, [evaluate=true])

[] marks optional arguments

Argumente

  • layer - The layer (or its ID or name)

  • feature - The feature which should be evaluated.

  • evaluate - If the expression must be evaluated. If false, the expression will be returned as a string literal only (which could potentially be later evaluated using the «eval» function).

Exemple

  • display_expression( 'streets', get_feature_by_id('streets', 1)) → The display expression of the feature with the ID 1 on the layer «streets».

  • display_expression('a_layer_id', @feature, 'False') → The display expression of the given feature not evaluated.

13.2.22.5. feature_id

Returns a feature’s unique ID, or NULL if the feature is not valid.

Sintaxă

feature_id(feature)

Argumente

  • feature - a feature object

Exemple

  • feature_id( @feature ) → the ID of the current feature

Further reading: get_feature_by_id

13.2.22.6. get_feature

Returns the first feature of a layer matching a given attribute value.

Single value variant

Along with the layer ID, a single column and value are specified.

Sintaxă

get_feature(layer, attribute, value)

Argumente

  • layer - layer name or ID

  • attribute - attribute name to use for the match

  • value - attribute value to match

Exemple

  • get_feature('streets','name','main st') → first feature found in „streets” layer with „main st” value in the „name” field

Map variant

Along with the layer ID, a map containing the columns (key) and their respective value to be used.

Sintaxă

get_feature(layer, attribute)

Argumente

  • layer - layer name or ID

  • attribute - Map containing the column and value pairs to use

Exemple

  • get_feature('streets',map('name','main st','lane_num','4')) → first feature found in „streets” layer with „main st” value in the „name” field and „4” value in the „lane_num” field

13.2.22.7. get_feature_by_id

Returns the feature with an id on a layer.

Sintaxă

get_feature_by_id(layer, feature_id)

Argumente

  • layer - layer, layer name or layer id

  • feature_id - the id of the feature which should be returned

Exemple

  • get_feature_by_id('streets', 1) → the feature with the id 1 on the layer „streets”

Further reading: feature_id

13.2.22.8. $id

Returns the feature id of the current row. WARNING: This function is deprecated. It is recommended to use the replacement @id variable instead.

Sintaxă

$id

Exemple

  • $id → 42

Further reading: feature_id, get_feature_by_id

13.2.22.9. is_attribute_valid

Returns TRUE if a specific feature attribute meets all constraints.

Sintaxă

is_attribute_valid(attribute, [feature], [layer], [strength])

[] marks optional arguments

Argumente

  • attribute - an attribute name

  • feature - A feature. If not set, the current feature will be used.

  • layer - A vector layer. If not set, the current layer will be used.

  • strength - Set to «hard» or «soft» to narrow down to a specific constraint type. If not set, the function will return FALSE if either a hard or a soft constraint fails.

Exemple

  • is_attribute_valid('HECTARES') → TRUE if the current feature’s value in the „HECTARES” field meets all constraints.

  • is_attribute_valid('HOUSES',get_feature('my_layer', 'FID', 10), 'my_layer') → FALSE if the value in the „HOUSES” field from the feature with „FID”=10 in «my_layer» fails to meet all constraints.

Further reading: Constraints

13.2.22.10. is_feature_valid

Returns TRUE if a feature meets all field constraints.

Sintaxă

is_feature_valid([feature], [layer], [strength])

[] marks optional arguments

Argumente

  • feature - A feature. If not set, the current feature will be used.

  • layer - A vector layer. If not set, the current layer will be used.

  • strength - Set to «hard» or «soft» to narrow down to a specific constraint type. If not set, the function will return FALSE if either a hard or a soft constraint fails.

Exemple

  • is_feature_valid(strength:='hard') → TRUE if all fields from the current feature meet their hard constraints.

  • is_feature_valid(get_feature('my_layer', 'FID', 10), 'my_layer') → FALSE if all fields from feature with „FID”=10 in «my_layer» fails to meet all constraints.

Further reading: Constraints

13.2.22.11. is_selected

Returns TRUE if a feature is selected. Can be used with zero, one or two arguments, see below for details.

No parameters

If called with no parameters, the function will return TRUE if the current feature in the current layer is selected.

Sintaxă

is_selected()

Exemple

  • is_selected() → TRUE if the current feature in the current layer is selected.

One «feature» parameter

If called with a «feature» parameter only, the function returns TRUE if the specified feature from the current layer is selected.

Sintaxă

is_selected(feature)

Argumente

  • feature - The feature which should be checked for selection.

Exemple

  • is_selected(@atlas_feature) → TRUE if the current atlas feature is selected.

  • is_selected(get_feature('streets', 'name', 'Main St.')) → TRUE if the unique named „Main St.” feature on the active „streets” layer is selected.

  • is_selected(get_feature_by_id('streets', 1)) → TRUE if the feature with the id 1 on the active „streets” layer is selected.

Two parameters

If the function is called with both a layer and a feature, it will return TRUE if the specified feature from the specified layer is selected.

Sintaxă

is_selected(layer, feature)

Argumente

  • layer - The layer (its ID or name) on which the selection will be checked.

  • feature - The feature which should be checked for selection.

Exemple

  • is_selected( 'streets', get_feature('streets', 'name', "street_name")) → TRUE if the current building’s street is selected (assuming the building layer has a field named «street_name» and the «streets» layer has a field called «name» with unique values).

  • is_selected( 'streets', get_feature_by_id('streets', 1)) → TRUE if the feature with the id 1 on the „streets” layer is selected.

13.2.22.12. maptip

Returns the maptip for a given feature in a layer. The expression is evaluated by default. Can be used with zero, one or more arguments, see below for details.

No parameters

If called with no parameters, the function will evaluate the maptip of the current feature in the current layer.

Sintaxă

maptip()

Exemple

  • maptip() → The maptip of the current feature in the current layer.

One «feature» parameter

If called with a «feature» parameter only, the function will evaluate the specified feature from the current layer.

Sintaxă

maptip(feature)

Argumente

  • feature - The feature which should be evaluated.

Exemple

  • maptip(@atlas_feature) → The maptip of the current atlas feature.

Layer and feature parameters

If the function is called with both a layer and a feature, it will evaluate the specified feature from the specified layer.

Sintaxă

maptip(layer, feature, [evaluate=true])

[] marks optional arguments

Argumente

  • layer - The layer (or its ID or name)

  • feature - The feature which should be evaluated.

  • evaluate - If the expression must be evaluated. If false, the expression will be returned as a string literal only (which could potentially be later evaluated using the «eval_template» function).

Exemple

  • maptip('streets', get_feature_by_id('streets', 1)) → The maptip of the feature with the ID 1 on the layer «streets».

  • maptip('a_layer_id', @feature, 'False') → The maptip of the given feature not evaluated.

13.2.22.13. num_selected

Returns the number of selected features on a given layer. By default works on the layer on which the expression is evaluated.

Sintaxă

num_selected([layer=current layer])

[] marks optional arguments

Argumente

  • layer - The layer (or its id or name) on which the selection will be checked.

Exemple

  • num_selected() → The number of selected features on the current layer.

  • num_selected('streets') → The number of selected features on the layer streets

13.2.22.14. represent_attributes

Returns a map with the attribute names as keys and the configured representation values as values. The representation value for the attributes depends on the configured widget type for each attribute. Can be used with zero, one or more arguments, see below for details.

No parameters

If called with no parameters, the function will return the representation of the attributes of the current feature in the current layer.

Sintaxă

represent_attributes()

Exemple

  • represent_attributes() → The representation of the attributes for the current feature.

One «feature» parameter

If called with a «feature» parameter only, the function will return the representation of the attributes of the specified feature from the current layer.

Sintaxă

represent_attributes(feature)

Argumente

  • feature - The feature which should be evaluated.

Exemple

  • represent_attributes(@atlas_feature) → The representation of the attributes for the specified feature from the current layer.

Layer and feature parameters

If called with a «layer» and a «feature» parameter, the function will return the representation of the attributes of the specified feature from the specified layer.

Sintaxă

represent_attributes(layer, feature)

Argumente

  • layer - The layer (or its ID or name).

  • feature - The feature which should be evaluated.

Exemple

  • represent_attributes('atlas_layer', @atlas_feature) → The representation of the attributes for the specified feature from the specified layer.

Mai multe detalii: represent_value

13.2.22.15. represent_value

Returns the configured representation value for a field value. It depends on the configured widget type. Often, this is useful for «Value Map» widgets.

Sintaxă

represent_value(value, [fieldName])

[] marks optional arguments

Argumente

  • value - The value which should be resolved. Most likely a field.

  • fieldName - The field name for which the widget configuration should be loaded.

Exemple

  • represent_value("field_with_value_map") → Description for value

  • represent_value('static value', 'field_name') → Description for static value

Mai multe detalii: widget types, represent_attributes

13.2.22.16. sqlite_fetch_and_increment

Manage autoincrementing values in sqlite databases.

SQlite default values can only be applied on insert and not prefetched.

This makes it impossible to acquire an incremented primary key via AUTO_INCREMENT before creating the row in the database. Sidenote: with postgres, this works via the option evaluate default values.

When adding new features with relations, it is really nice to be able to already add children for a parent, while the parents form is still open and hence the parent feature uncommitted.

To get around this limitation, this function can be used to manage sequence values in a separate table on sqlite based formats like gpkg.

The sequence table will be filtered for a sequence id (filter_attribute and filter_value) and the current value of the id_field will be incremented by 1 and the incremented value returned.

If additional columns require values to be specified, the default_values map can be used for this purpose.

Note

This function modifies the target sqlite table. It is intended for usage with default value configurations for attributes.

When the database parameter is a layer and the layer is in transaction mode, the value will only be retrieved once during the lifetime of a transaction and cached and incremented. This makes it unsafe to work on the same database from several processes in parallel.

Sintaxă

sqlite_fetch_and_increment(database, table, id_field, filter_attribute, filter_value, [default_values])

[] marks optional arguments

Argumente

  • database - Path to the sqlite file or geopackage layer

  • table - Name of the table that manages the sequences

  • id_field - Name of the field that contains the current value

  • filter_attribute - Name the field that contains a unique identifier for this sequence. Must have a UNIQUE index.

  • filter_value - Name of the sequence to use.

  • default_values - Map with default values for additional columns on the table. The values need to be fully quoted. Functions are allowed.

Exemple

  • sqlite_fetch_and_increment(@layer, 'sequence_table', 'last_unique_id', 'sequence_id', 'global', map('last_change', 'date(''now'')', 'user', '''' || @user_account_name || '''')) → 0

  • sqlite_fetch_and_increment(layer_property(@layer, 'path'), 'sequence_table', 'last_unique_id', 'sequence_id', 'global', map('last_change', 'date(''now'')', 'user', '''' || @user_account_name || '''')) → 0

Mai multe detalii: Data Sources Properties, Setting relations between multiple layers

13.2.22.17. uuid

Generates a Universally Unique Identifier (UUID) for each row using the Qt QUuid::createUuid method.

Sintaxă

uuid([format=»WithBraces»])

[] marks optional arguments

Argumente

  • format - The format, as the UUID will be formatted. «WithBraces», «WithoutBraces» or «Id128».

Exemple

  • uuid() → «{0bd2f60f-f157-4a6d-96af-d4ba4cb366a1}»

  • uuid('WithoutBraces') → «0bd2f60f-f157-4a6d-96af-d4ba4cb366a1»

  • uuid('Id128') → «0bd2f60ff1574a6d96afd4ba4cb366a1»

13.2.23. Relations

This group contains the list of the relations available in the current project, with their description. It provides a quick access to the relation ID for writing an expression (with e.g. the relation_aggregate function) or customizing a form.

13.2.24. Sensors Functions

This group contains functions to interact with sensors.

13.2.24.1. sensor_data

Returns the last captured value (or values as a map for sensors which report multiple values) from a registered sensor.

Sintaxă

sensor_data(name, [expiration])

[] marks optional arguments

Argumente

  • name - the sensor name

  • expiration - maximum millisecond since last captured value allowed

Exemple

  • sensor_data('geiger_1') → «2000»

13.2.25. Funcții pentru Șiruri

Acest grup conține funcții care operează asupra șirurilor, (de ex: înlocuirea, conversia în majuscule).

13.2.25.1. ascii

Returns the unicode code associated with the first character of a string.

Sintaxă

ascii(string)

Argumente

  • string - the string to convert to unicode code

Exemple

  • ascii('Q') → 81

13.2.25.2. char

Returns the character associated with a unicode code.

Sintaxă

char(code)

Argumente

  • code - a unicode code number

Exemple

  • char(81) → «Q»

13.2.25.3. concat

Concatenates several strings to one. NULL values are converted to empty strings. Other values (like numbers) are converted to strings.

Sintaxă

concat(string1, string2, …)

Argumente

  • string - a string value

Exemple

  • concat('sun', 'set') → «sunset»

  • concat('a','b','c','d','e') → «abcde»

  • concat('Anno ', 1984) → «Anno 1984»

  • concat('The Wall', NULL) → «The Wall»

About fields concatenation

You can also concatenate strings or field values using either || or + operators, with some special characteristics:

  • The + operator also means sum up expression, so if you have an integer (field or numeric value) operand, this can be error prone and you better use the others:

    'My feature id is: ' + "gid" => triggers an error as gid returns an integer
    
  • When any of the arguments is a NULL value, either || or + will return a NULL value. To return the other arguments regardless the NULL value, you may want to use the concat function:

    'My feature id is: ' + NULL ==> NULL
    'My feature id is: ' || NULL => NULL
    concat('My feature id is: ', NULL) => 'My feature id is: '
    

mai multe detalii: ||, +

13.2.25.4. format

Format a string using supplied arguments.

Sintaxă

format(string, arg1, arg2, …)

Argumente

  • string - A string with placeholders %1, %2, etc., for the arguments. Placeholders can be repeated. The lowest numbered placeholder is replaced by arg1, the next by arg2, etc.

  • arg - any type. Any number of arguments.

Exemple

  • format('This %1 a %2','is', 'test') → «This is a test»

  • format('This is %2','a bit unexpected but 2 is lowest number in string','normal') → «This is a bit unexpected but 2 is lowest number in string»

13.2.25.5. format_date

Formats a date type or string into a custom string format. Uses Qt date/time format strings. See QDateTime::toString.

Sintaxă

format_date(datetime, format, [language])

[] marks optional arguments

Argumente

  • datetime - date, time or datetime value

  • format - String template used to format the string.

    Expression

    Rezultat

    d

    ziua, un număr fără zero la început (de la 1 la 31)

    dd

    ziua, un număr cu zero la început (de la 01 la 31)

    ddd

    the abbreviated localized day name (e.g. «Mon» to «Sun»)

    dddd

    the long localized day name (e.g. «Monday» to «Sunday»)

    M

    the month as number without a leading zero (1-12)

    MM

    the month as number with a leading zero (01-12)

    MMM

    the abbreviated localized month name (e.g. «Jan» to «Dec»)

    MMMM

    the long localized month name (e.g. «January» to «December»)

    yy

    the year as two digit number (00-99)

    yyyy

    the year as four digit number

    These expressions may be used for the time part of the format string:

    Expression

    Rezultat

    h

    the hour without a leading zero (0 to 23 or 1 to 12 if AM/PM display)

    hh

    the hour with a leading zero (00 to 23 or 01 to 12 if AM/PM display)

    H

    the hour without a leading zero (0 to 23, even with AM/PM display)

    HH

    the hour with a leading zero (00 to 23, even with AM/PM display)

    m

    minutul, fără zero la început (de la 0 la 59)

    mm

    minutul, cu zero la început (de la 00 la 59)

    s

    secunda, fără zero la început (de la 0 la 59)

    ss

    secunda, cu un zero la început (de la 00 la 59)

    z

    the milliseconds without trailing zeroes (0 to 999)

    zzz

    the milliseconds with trailing zeroes (000 to 999)

    AP or A

    interpret as an AM/PM time. AP must be either «AM» or «PM».

    ap or a

    Interpret as an AM/PM time. ap must be either «am» or «pm».

  • language - language (lowercase, two- or three-letter, ISO 639 language code) used to format the date into a custom string. By default the current QGIS user locale is used.

Exemple

  • format_date('2012-05-15','dd.MM.yyyy') → «15.05.2012»

  • format_date('2012-05-15','d MMMM yyyy','fr') → «15 mai 2012»

  • format_date('2012-05-15','dddd') → «Tuesday», if the current locale is an English variant

  • format_date('2012-05-15 13:54:20','dd.MM.yy') → «15.05.12»

  • format_date('13:54:20','hh:mm AP') → «01:54 PM»

13.2.25.6. format_number

Returns a number formatted with the locale separator for thousands. By default the current QGIS user locale is used. Also truncates the decimal places to the number of supplied places.

Sintaxă

format_number(number, [places=0], [language], [omit_group_separators=false], [trim_trailing_zeroes=false])

[] marks optional arguments

Argumente

  • number - number to be formatted

  • places - integer representing the number of decimal places to truncate the string to.

  • language - language (lowercase, two- or three-letter, ISO 639 language code) used to format the number into a string. By default the current QGIS user locale is used.

  • omit_group_separators - if set to true then group separators will not be included in the string

  • trim_trailing_zeroes - if set to true then trailing zeros following the decimal point will be trimmed from the string

Exemple

  • format_number(10000000.332,2) → «10,000,000.33» if e.g. the current locale is an English variant

  • format_number(10000000.332,2,'fr') → «10 000 000,33»

13.2.25.7. left

Returns a substring that contains the n leftmost characters of the string.

Sintaxă

left(string, length)

Argumente

  • string - a string

  • length - integer. The number of characters from the left of the string to return.

Exemple

  • left('Hello World',5) → «Hello»

13.2.25.8. length

Returns the number of characters in a string or the length of a geometry linestring.

String variant

Returns the number of characters in a string.

Sintaxă

length(string)

Argumente

  • string - string to count length of

Exemple

  • length('hello') → 5

Geometry variant

Calculate the length of a geometry line object. Calculations are always planimetric in the Spatial Reference System (SRS) of this geometry, and the units of the returned length will match the units for the SRS. This differs from the calculations performed by the $length function, which will perform ellipsoidal calculations based on the project’s ellipsoid and distance unit settings.

Sintaxă

length(geometry)

Argumente

  • geometry - line geometry object

Exemple

  • length(geom_from_wkt('LINESTRING(0 0, 4 0)')) → 4.0

13.2.25.9. lower

Converts a string to lower case letters.

Sintaxă

lower(string)

Argumente

  • string - the string to convert to lower case

Exemple

  • lower('HELLO World') → «hello world»

13.2.25.10. lpad

Returns a string padded on the left to the specified width, using a fill character. If the target width is smaller than the string’s length, the string is truncated.

Sintaxă

lpad(string, width, fill)

Argumente

  • string - string to pad

  • width - length of new string

  • fill - character to pad the remaining space with

Exemple

  • lpad('Hello', 10, 'x') → «xxxxxHello»

  • lpad('Hello', 3, 'x') → «Hel»

13.2.25.11. ltrim

Removes the longest string containing only the specified characters (a space by default) from the start of string.

Sintaxă

ltrim(string, [characters=» «])

[] marks optional arguments

Argumente

  • string - string to trim

  • characters - characters to trim

Exemple

  • ltrim('   hello world  ') → «hello world «

  • ltrim('zzzytest', 'xyz') → «test»

Further reading: rtrim, trim

13.2.25.12. regexp_match

Return the first matching position matching a regular expression within an unicode string, or 0 if the substring is not found.

Sintaxă

regexp_match(input_string, regex)

Argumente

  • input_string - the string to test against the regular expression

  • regex - The regular expression to test against. Backslash characters must be double escaped (e.g., „\\s” to match a white space character or „\\b” to match a word boundary).

Exemple

  • regexp_match('QGIS ROCKS','\\sROCKS') → 5

  • regexp_match('Budač','udač\\b') → 2

13.2.25.13. regexp_replace

Returns a string with the supplied regular expression replaced.

Sintaxă

regexp_replace(input_string, regex, replacement)

Argumente

  • input_string - the string to replace matches in

  • regex - The regular expression to replace. Backslash characters must be double escaped (e.g., „\\s” to match a white space character).

  • replacement - The string that will replace any matching occurrences of the supplied regular expression. Captured groups can be inserted into the replacement string using \\1, \\2, etc.

Exemple

  • regexp_replace('QGIS SHOULD ROCK','\\sSHOULD\\s',' DOES ') → «QGIS DOES ROCK»

  • regexp_replace('ABC123','\\d+','') → «ABC»

  • regexp_replace('my name is John','(.*) is (.*)','\\2 is \\1') → «John is my name»

13.2.25.14. regexp_substr

Returns the portion of a string which matches a supplied regular expression.

Sintaxă

regexp_substr(input_string, regex)

Argumente

  • input_string - the string to find matches in

  • regex - The regular expression to match against. Backslash characters must be double escaped (e.g., „\\s” to match a white space character).

Exemple

  • regexp_substr('abc123','(\\d+)') → «123»

13.2.25.15. replace

Returns a string with the supplied string, array, or map of strings replaced.

String & array variant

Returns a string with the supplied string or array of strings replaced by a string or an array of strings.

Sintaxă

replace(string, before, after)

Argumente

  • string - șirul de intrare

  • before - the string or array of strings to replace

  • after - the string or array of strings to use as a replacement

Exemple

  • replace('QGIS SHOULD ROCK','SHOULD','DOES') → «QGIS DOES ROCK»

  • replace('QGIS ABC',array('A','B','C'),array('X','Y','Z')) → «QGIS XYZ»

  • replace('QGIS',array('Q','S'),'') → «GI»

Map variant

Returns a string with the supplied map keys replaced by paired values. Longer map keys are evaluated first.

Sintaxă

replace(string, map)

Argumente

  • string - șirul de intrare

  • map - the map containing keys and values

Exemple

  • replace('APP SHOULD ROCK',map('APP','QGIS','SHOULD','DOES')) → «QGIS DOES ROCK»

  • replace('forty two',map('for','4','two','2','forty two','42')) → «42»

13.2.25.17. rpad

Returns a string padded on the right to the specified width, using a fill character. If the target width is smaller than the string’s length, the string is truncated.

Sintaxă

rpad(string, width, fill)

Argumente

  • string - string to pad

  • width - length of new string

  • fill - character to pad the remaining space with

Exemple

  • rpad('Hello', 10, 'x') → «Helloxxxxx»

  • rpad('Hello', 3, 'x') → «Hel»

13.2.25.18. rtrim

Removes the longest string containing only the specified characters (a space by default) from the end of string.

Sintaxă

rtrim(string, [characters=» «])

[] marks optional arguments

Argumente

  • string - string to trim

  • characters - characters to trim

Exemple

  • rtrim('   hello world  ') → « hello world»

  • rtrim('testxxzx', 'xyz') → «test»

Further reading: ltrim, trim

13.2.25.19. strpos

Return the first matching position of a substring within another string, or 0 if the substring is not found.

Sintaxă

strpos(haystack, needle)

Argumente

  • haystack - string that is to be searched

  • needle - string to search for

Exemple

  • strpos('HELLO WORLD','WORLD') → 7

  • strpos('HELLO WORLD','GOODBYE') → 0

13.2.25.20. substr

Returns a part of a string.

Sintaxă

substr(string, start, [length])

[] marks optional arguments

Argumente

  • string - the full input string

  • start - integer representing start position to extract beginning with 1; if start is negative, the return string will begin at the end of the string minus the start value

  • length - integer representing length of string to extract; if length is negative, the return string will omit the given length of characters from the end of the string

Exemple

  • substr('HELLO WORLD',3,5) → «LLO W»

  • substr('HELLO WORLD',6) → « WORLD»

  • substr('HELLO WORLD',-5) → «WORLD»

  • substr('HELLO',3,-1) → «LL»

  • substr('HELLO WORLD',-5,2) → «WO»

  • substr('HELLO WORLD',-5,-1) → «WORL»

13.2.25.21. title

Converts all words of a string to title case (all words lower case with leading capital letter).

Sintaxă

title(string)

Argumente

  • string - the string to convert to title case

Exemple

  • title('hello WOrld') → «Hello World»

13.2.25.22. to_string

Convertește un număr într-un șir.

Sintaxă

to_string(number)

Argumente

  • number - Număr întreg sau valoare reală. Numărul de convertit în șir.

Exemple

  • to_string(123) → «123»

13.2.25.23. trim

Removes all leading and trailing whitespace (spaces, tabs, etc) from a string.

Sintaxă

trim(string)

Argumente

  • string - string to trim

Exemple

  • trim('   hello world  ') → «hello world»

Further reading: ltrim, rtrim

13.2.25.24. upper

Converts a string to upper case letters.

Sintaxă

upper(string)

Argumente

  • string - the string to convert to upper case

Exemple

  • upper('hello WOrld') → «HELLO WORLD»

13.2.25.25. wordwrap

Returns a string wrapped to a maximum/minimum number of characters.

Sintaxă

wordwrap(string, wrap_length, [delimiter_string])

[] marks optional arguments

Argumente

  • string - the string to be wrapped

  • wrap_length - an integer. If wrap_length is positive the number represents the ideal maximum number of characters to wrap; if negative, the number represents the minimum number of characters to wrap.

  • delimiter_string - Optional delimiter string to wrap to a new line.

Exemple

  • wordwrap('UNIVERSITY OF QGIS',13) → «UNIVERSITY OF<br>QGIS»

  • wordwrap('UNIVERSITY OF QGIS',-3) → «UNIVERSITY<br>OF QGIS»

13.2.26. User Expressions

This group contains the expressions saved as user expressions.

13.2.27. Variabile

This group contains dynamic variables related to the application, the project file and other settings. The availability of variables depends on the context:

  • din dialogul expressionSelect Select by expression

  • din dialogul calculateField Field calculator

  • din dialogul cu proprietățile stratului

  • from the print layout

To use these variables in an expression, they should be preceded by the @ character (e.g, @row_number).

Variable

Descriere

algorithm_id

The unique ID of an algorithm

animation_end_time

End of the animation’s overall temporal time range (as a datetime value)

animation_interval

Duration of the animation’s overall temporal time range (as an interval value)

animation_start_time

Start of the animation’s overall temporal time range (as a datetime value)

atlas_feature

The current atlas feature (as feature object)

atlas_featureid

The current atlas feature ID

atlas_featurenumber

The current atlas feature number in the layout

atlas_filename

The current atlas file name

atlas_geometry

The current atlas feature geometry

atlas_layerid

The current atlas coverage layer ID

atlas_layername

The current atlas coverage layer name

atlas_pagename

The current atlas page name

atlas_totalfeatures

The total number of features in atlas

canvas_cursor_point

The last cursor position on the canvas in the project’s geographical coordinates

cluster_color

The color of symbols within a cluster, or NULL if symbols have mixed colors

cluster_size

The number of symbols contained within a cluster

current_feature

The feature currently being edited in the attribute form or table row

current_geometry

The geometry of the feature currently being edited in the form or the table row

current_parent_feature

represents the feature currently being edited in the parent form. Only usable in an embedded form context.

current_parent_geometry

represents the geometry of the feature currently being edited in the parent form. Only usable in an embedded form context.

form_mode

What the form is used for, like AddFeatureMode, SingleEditMode, MultiEditMode, SearchMode, AggregateSearchMode or IdentifyMode as string.

feature

The current feature being evaluated. This can be used with the «attribute» function to evaluate attribute values from the current feature.

frame_duration

Temporal duration of each animation frame (as an interval value)

frame_number

Current frame number during animation playback

frame_rate

Number of frames per second during animation playback

fullextent_maxx

Maximum x value from full canvas extent (including all layers)

fullextent_maxy

Maximum y value from full canvas extent (including all layers)

fullextent_minx

Minimum x value from full canvas extent (including all layers)

fullextent_miny

Minimum y value from full canvas extent (including all layers)

geometrie

The geometry of the current feature being evaluated

geometry_part_count

The number of parts in rendered feature’s geometry

geometry_part_num

The current geometry part number for feature being rendered

geometry_point_count

The number of points in the rendered geometry’s part

geometry_point_num

The current point number in the rendered geometry’s part

geometry_ring_num

Current geometry ring number for feature being rendered (for polygon features only). The exterior ring has a value of 0.

grid_axis

The current grid annotation axis (eg, «x» for longitude, «y» for latitude)

grid_number

The current grid annotation value

id

The ID of the current feature being evaluated

item_id

The layout item user ID (not necessarily unique)

item_uuid

The layout item unique ID

layer

The current layer

layer_crs

The Coordinate Reference System Authority ID of the current layer

layer_crs_ellipsoid

The ellipsoid Authority ID of the current layer CRS

layer_cursor_point

Point geometry under the mouse position in map canvas, in active layer’s CRS

layer_id

The ID of current layer

layer_ids

The IDs of all the map layers in the current project as a list

layer_name

The name of current layer

layers

All the map layers in the current project as a list

layout_dpi

The composition resolution (DPI)

layout_name

The layout name

layout_numpages

The number of pages in the layout

layout_page

The page number of the current item in the layout

layout_pageheight

The active page height in the layout (in mm for standard paper sizes, or whatever unit was used for custom paper size)

layout_pageoffsets

Array of Y coordinate of the top of each page. Allows to dynamically position items on pages in a context where page sizes may change

layout_pagewidth

The active page width in the layout (in mm for standard paper sizes, or whatever unit was used for custom paper size)

legend_column_count

The number of columns in the legend

legend_filter_by_map

Indicates if the content of the legend is filtered by the map

legend_filter_out_atlas

Indicates if the atlas is filtered out of the legend

legend_split_layers

Indicates if layers can be split in the legend

legend_title

The title of the legend

legend_wrap_string

The character(s) used to wrap the legend text

map_crs

The Coordinate reference system of the current map

map_crs_acronym

The acronym of the Coordinate reference system of the current map

map_crs_definition

The full definition of the Coordinate reference system of the current map

map_crs_description

The name of the Coordinate reference system of the current map

map_crs_ellipsoid

The acronym of the ellipsoid of the Coordinate reference system of the current map

map_crs_proj4

The Proj4 definition of the Coordinate reference system of the current map

map_crs_projection

The descriptive name of the projection method used by the Coordinate reference system of the map (e.g. «Albers Equal Area»)

map_crs_wkt

The WKT definition of the Coordinate reference system of the current map

map_end_time

The end of the map’s temporal time range (as a datetime value)

map_extent

The geometry representing the current extent of the map

map_extent_center

The point feature at the center of the map

map_extent_height

The current height of the map

map_extent_width

The current width of the map

map_id

The ID of current map destination. This will be «canvas» for canvas renders, and the item ID for layout map renders

map_interval

The duration of the map’s temporal time range (as an interval value)

map_layer_ids

The list of map layer IDs visible in the map

map_layers

The list of map layers visible in the map

map_rotation

The current rotation of the map

map_scale

The current scale of the map

map_start_time

The start of the map’s temporal time range (as a datetime value)

map_units

The units of map measurements

model_path

Full path (including file name) of current model (or project path if model is embedded in a project).

model_folder

Folder containing current model (or project folder if model is embedded in a project).

model_name

Name of current model

model_group

Group for current model

notification_message

Content of the notification message sent by the provider (available only for actions triggered by provider notifications).

parent

Refers to the current feature in the parent layer, providing access to its attributes and geometry when filtering an aggregate function

project_abstract

The project abstract, taken from project metadata

project_area_units

The area unit for the current project, used when calculating areas of geometries

project_author

The project author, taken from project metadata

project_basename

The basename of current project’s filename (without path and extension)

project_creation_date

The project creation date, taken from project metadata

project_crs

The Coordinate reference system of the project

project_crs_arconym

The acronym of the Coordinate reference system of the project

project_crs_definition

The full definition of the Coordinate reference system of the project

project_crs_description

The description of the Coordinate reference system of the project

project_crs_ellipsoid

The ellipsoid of the Coordinate reference system of the project

project_crs_proj4

The Proj4 representation of the Coordinate reference system of the project

project_crs_wkt

The WKT (well known text) representation of the coordinate reference system of the project

project_distance_units

The distance unit for the current project, used when calculating lengths of geometries and distances

project_ellipsoid

The name of the ellipsoid of the current project, used when calculating geodetic areas or lengths of geometries

project_filename

The filename of the current project

project_folder

The folder of the current project

project_home

The home path of the current project

project_identifier

The project identifier, taken from the project’s metadata

project_keywords

The project keywords, taken from the project’s metadata

project_last_saved

Date/time when project was last saved.

project_path

The full path (including file name) of the current project

project_title

The title of current project

project_units

The units of the project’s CRS

qgis_locale

The current language of QGIS

qgis_os_name

The current Operating system name, eg «windows», «linux» or «osx»

qgis_platform

The QGIS platform, eg «desktop» or «server»

qgis_release_name

The current QGIS release name

qgis_short_version

The current QGIS version short string

qgis_version

The current QGIS version string

qgis_version_no

The current QGIS version number

row_number

Stochează numărul rândului curent

snapping_results

Gives access to snapping results while digitizing a feature (only available in add feature)

scale_value

The current scale bar distance value

selected_file_path

Selected file path from file widget selector when uploading a file with an external storage system

symbol_angle

The angle of the symbol used to render the feature (valid for marker symbols only)

symbol_color

The color of the symbol used to render the feature

symbol_count

The number of features represented by the symbol (in the layout legend)

symbol_frame

The frame number (for animated symbols only)

symbol_id

The Internal ID of the symbol (in the layout legend)

symbol_label

The label for the symbol (either a user defined label or the default autogenerated label - in the layout legend)

symbol_layer_count

Total number of symbol layers in the symbol

symbol_layer_index

Current symbol layer index

symbol_marker_column

Column number for marker (valid for point pattern fills only).

symbol_marker_row

Row number for marker (valid for point pattern fills only).

user_account_name

The current user’s operating system account name

user_full_name

The current user’s operating system user name

valoare

The current value

vector_tile_zoom

Exact vector tile zoom level of the map that is being rendered (derived from the current map scale). Normally in interval [0, 20]. Unlike @zoom_level, this variable is a floating point value which can be used to interpolate values between two integer zoom levels.

with_variable

Allows setting a variable for usage within an expression and avoid recalculating the same value repeatedly

zoom_level

Vector tile zoom level of the map that is being rendered (derived from the current map scale). Normally in interval [0, 20].

Câteva exemple:

  • Return the X coordinate of a map item center in layout:

    x( map_get( item_variables( 'map1'), 'map_extent_center' ) )
    
  • Return, for each feature in the current layer, the number of overlapping airport features:

    aggregate( layer:='airport', aggregate:='count', expression:="code",
                   filter:=intersects( $geometry, geometry( @parent ) ) )
    
  • Get the object_id of the first snapped point of a line:

    with_variable(
      'first_snapped_point',
      array_first( @snapping_results ),
      attribute(
        get_feature_by_id(
          map_get( @first_snapped_point, 'layer' ),
          map_get( @first_snapped_point, 'feature_id' )
        ),
        'object_id'
      )
    )
    

13.2.28. Funcții Recente

This group contains recently used functions. Depending on the context of its usage (feature selection, field calculator, generic), recently applied expressions are added to the corresponding list (up to ten expressions), sorted from more to less recent. This makes it easy to quickly retrieve and reapply previously used expressions.