Vector selection

Extract by attribute

Creates two vector layers from an input layer: one will contain only matching features while the second will contain all the non-matching features.

The criteria for adding features to the resulting layer is defined based on the values of an attribute from the input layer.

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Layer to extract features from.
Selection attribute FIELD [tablefield: any] Filtering field of the layer
Operator OPERATOR

[enumeration]

Default: 0

Many different operators are available:

  • 0 — =
  • 1 — ≠
  • 2 — >
  • 3 — >=
  • 4 — <
  • 5 — <=
  • 6 — begins with
  • 7 — contains
  • 8 — is null
  • 9 — is not null
  • 10 — does not contain

Value

Optional

VALUE [string] Value to be evaluated
Extracted (attribute) OUTPUT

[same as input]

Default: [Create Temporary Layer]

Specify the output vector layer for matching features. One of:

  • Create Temporary Layer (TEMPORARY_OUTPUT)
  • Save to File…
  • Save to Geopackage…
  • Save to PostGIS Table

The file encoding can also be changed here.

Extracted (non-matching) FAIL_OUTPUT

[same as input]

Default: [Skip output]

Specify the output vector layer for non-matching features. One of:

  • Skip Output
  • Create Temporary Layer (TEMPORARY_OUTPUT)
  • Save to File…
  • Save to Geopackage…
  • Save to PostGIS Table

Outputs

Label Name Type Description
Extracted (attribute) OUTPUT [same as input] Vector layer with matching features from the input layer
Extracted (non-matching) FAIL_OUTPUT [same as input] Vector layer with non-matching features from the input layer

Extract by expression

Creates two vector layers from an input layer: one will contain only matching features while the second will contain all the non-matching features.

The criteria for adding features to the resulting layer is based on a QGIS expression.

For more information about expressions see the Expressions.

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Input vector layer
Expression EXPRESSION [expression] Expression to filter the vector layer
Matching features OUTPUT

[same as input]

Default: [Create Temporary Layer]

Specify the output vector layer for matching features. One of:

  • Create Temporary Layer (TEMPORARY_OUTPUT)
  • Save to File…
  • Save to Geopackage…
  • Save to PostGIS Table

The file encoding can also be changed here.

Non-matching FAIL_OUTPUT

[same as input]

Default: [Skip output]

Specify the output vector layer for non-matching features. One of:

  • Skip Output
  • Create Temporary Layer (TEMPORARY_OUTPUT)
  • Save to File…
  • Save to Geopackage…
  • Save to PostGIS Table

Outputs

Label Name Type Description
Matching features OUTPUT [same as input] Vector layer with matching features from the input layer
Non-matching FAIL_OUTPUT [same as input] Vector layer with non-matching features from the input layer

Extract by location

Creates a new vector layer that only contains matching features from an input layer.

The criteria for adding features to the resulting layer is defined based on the spatial relationship between each feature and the features in an additional layer.

Parameters

Label Name Type Description
Extract features from INPUT [vector: any] Input vector layer
Where the features (geometric predicate) PREDICATE

[enumeration] [list]

Default: [0]

Spatial condition for the selection. One or more of:

  • 0 — intersect
  • 1 — contain
  • 2 — disjoint
  • 3 — equal
  • 4 — touch
  • 5 — overlap
  • 6 — are within
  • 7 — cross

If more than one condition is chosen, at least one of them (OR operation) has to be met for a feature to be extracted.

By comparing to the features from INTERSECT [vector: any] Intersection vector layer
Extracted (location) OUTPUT

[same as input]

Default: [Create temporary layer]

Specify the output vector layer for the features that have the chosen spatial relationship(s) with one or more features in the comparison layer. One of:

  • Create Temporary Layer (TEMPORARY_OUTPUT)
  • Save to File…
  • Save to Geopackage…
  • Save to PostGIS Table

Outputs

Label Name Type Description
Extracted (location) OUTPUT [same as input] Vector layer with features from the input layer that have the chosen spatial relationship(s) with one or more features in the comparison layer.

Random extract

Takes a vector layer and generates a new one that contains only a subset of the features in the input layer.

The subset is defined randomly, based on feature IDs, using a percentage or count value to define the total number of features in the subset.

See also

Random selection

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Source vector layer to select the features from
Method METHOD

[enumeration]

Default: 0

Random selection methodn. One of:

  • 0 — Number of selected features
  • 1 — Percentage of selected features
Number/percentage of selected features NUMBER

[number]

Default: 10

Number or percentage of features to select
Extracted (random) OUTPUT

[vector: any]

Default: [Create temporary layer]

Specify the output vector layer for the randomly selected features. One of:

  • Create Temporary Layer (TEMPORARY_OUTPUT)
  • Save to File…
  • Save to Geopackage…
  • Save to PostGIS Table

Vector layer containing randomly selected features

Outputs

Label Name Type Description
Extracted (random) OUTPUT [same as input] Vector layer containing randomly selected features from the input layer

Random extract within subsets

Takes a vector layer and generates a new one that contains only a subset of the features in the input layer.

The subset is defined randomly, based on feature IDs, using a percentage or count value to define the total number of features in the subset. The percentage/count value is not applied to the whole layer, but instead to each category. Categories are defined according to a given attribute.

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Vector layer to select the features from
ID field FIELD [tablefield: any] Category of the source vector layer to select the features from
Method METHOD

[enumeration]

Default: 0

Random selection method. One of:

  • 0 — Number of selected features
  • 1 — Percentage of selected features
Number/percentage of selected features NUMBER

[number]

Default: 10

Number or percentage of features to select
Extracted (random stratified) OUTPUT

[same as input]

Default: [Create temporary layer]

Specify the output vector layer for the randomly selected features. One of:

  • Create Temporary Layer (TEMPORARY_OUTPUT)
  • Save to File…
  • Save to Geopackage…
  • Save to PostGIS Table

The file encoding can also be changed here.

Outputs

Label Name Type Description
Extracted (random stratified) OUTPUT [same as input] Vector layer containing randomly selected features from the input layer

Random selection

Takes a vector layer and selects a subset of its features. No new layer is generated by this algorithm.

The subset is defined randomly, based on feature IDs, using a percentage or count value to define the total number of features in the subset.

Default menu: Vector ‣ Research Tools

See also

Random extract

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Vector layer for the selection
Method METHOD

[enumeration]

Default: 0

Random selection method. One of:

  • 0 — Number of selected features
  • 1 — Percentage of selected features
Number/percentage of selected features NUMBER

[number]

Default: 10

Number or percentage of features to select

Outputs

Label Name Type Description
Input layer INPUT [same as input] The input layer with features selected

Random selection within subsets

Takes a vector layer and selects a subset of its features. No new layer is generated by this algorithm.

The subset is defined randomly, based on feature IDs, using a percentage or count value to define the total number of features in the subset.

The percentage/count value is not applied to the whole layer, but instead to each category.

Categories are defined according to a given attribute, which is also specified as an input parameter for the algorithm.

No new outputs are created.

Default menu: Vector ‣ Research Tools

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Vector layer to select features in
ID field FIELD [tablefield: any] Category of the input layer to select the features from
Method METHOD

[enumeration]

Default: 0

Random selection method. One of:

  • 0 — Number of selected features
  • 1 — Percentage of selected features
Number/percentage of selected features NUMBER

[number]

Default: 10

Number or percentage of features to select

Outputs

Label Name Type Description
Input layer INPUT [same as input] The input layer with features selected

Select by attribute

Creates a selection in a vector layer.

The criteria for selected features is defined based on the values of an attribute from the input layer.

No new outputs are created.

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Vector layer to select features in
Selection attribute FIELD [tablefield: any] Filtering field of the layer
Operator OPERATOR

[enumeration]

Default: 0

Many different operators are available:

  • 0 — =
  • 1 — ≠
  • 2 — >
  • 3 — >=
  • 4 — <
  • 5 — <=
  • 6 — begins with
  • 7 — contains
  • 8 — is null
  • 9 — is not null
  • 10 — does not contain

Value

Optional

VALUE [string] Value to be evaluated
Modify current selection by METHOD

[enumeration]

Default: 0

How the selection of the algorithm should be managed. One of:

  • 0 — creating new selection
  • 1 — adding to current selection
  • 2 — selecting within current selection
  • 3 — removing from current selection

Outputs

Label Name Type Description
Input layer INPUT [same as input] The input layer with features selected

Select by expression

Creates a selection in a vector layer. The criteria for selecting features is based on a QGIS expression. For more information about expressions see the Expressions.

No new outputs are created.

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Input vector layer
Expression EXPRESSION [expression] Expression to filter the input layer
Modify current selection by METHOD

[enumeration]

Default: 0

How the selection of the algorithm should be managed. One of:

  • 0 — creating new selection
  • 1 — adding to current selection
  • 2 — selecting within current selection
  • 3 — removing from current selection

Outputs

Label Name Type Description
Input layer INPUT [same as input] The input layer with features selected

Select by location

Creates a selection in a vector layer. The criteria for selecting features is based on the spatial relationship between each feature and the features in an additional layer.

No new outputs are created.

Default menu: Vector ‣ Research Tools

Parameters

Label Name Type Description
Select features from INPUT [vector: any] Input vector layer
Where the features (geometric predicate) PREDICATE

[enumeration] [list]

Default: [0]

Spatial condition for the selection. One or more of:

  • 0 — intersect
  • 1 — contain
  • 2 — disjoint
  • 3 — equal
  • 4 — touch
  • 5 — overlap
  • 6 — are within
  • 7 — cross

If more than one condition is chosen, at least one of them (OR operation) has to be met for a feature to be extracted.

By comparing to the features from INTERSECT [vector: any] Intersection vector layer
Modify current selection by METHOD

[enumeration]

Default: 0

How the selection of the algorithm should be managed. One of:

  • 0 — creating new selection
  • 1 — adding to current selection
  • 2 — selecting within current selection
  • 3 — removing from current selection

Outputs

Label Name Type Description
Input layer INPUT [same as input] The input layer with features selected