24.1.19. Vector table

24.1.19.1. Add autoincremental field

Adds a new integer field to a vector layer, with a sequential value for each feature.

This field can be used as a unique ID for features in the layer. The new attribute is not added to the input layer but a new layer is generated instead.

The initial starting value for the incremental series can be specified. Optionally, the incremental series can be based on grouping fields and a sort order for features can also be specified.

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: any]	The input vector layer.
Field name	FIELD_NAME	[string] Default: 'AUTO'	Name of the field with autoincremental values
Start values at Optional	START	[number] Default: 0	Choose the initial number of the incremental count
Group values by Optional	GROUP_FIELDS	[tablefield: any] [list]	Select grouping field(s): instead of a single count run for the whole layer, a separate count is processed for each value returned by the combination of these fields.
Sort expression Optional	SORT_EXPRESSION	[expression]	Use an expression to sort the features in the layer either globally or if set, based on group fields.
Sort ascending	SORT_ASCENDING	[boolean] Default: True	When a sort expression is set, use this option to control the order in which features are assigned values.
Sort nulls first	SORT_NULLS_FIRST	[boolean] Default: False	When a sort expression is set, use this option to set whether Null values are counted first or last.
Incremented	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer with the auto increment field. 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.

輸出

Label	名稱	Type	說明
Incremented	OUTPUT	[same as input]	Vector layer with auto incremental field

Python code

Algorithm ID: qgis:addautoincrementalfield

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

24.1.19.2. Add field to attributes table

Adds a new field to a vector layer.

The name and characteristics of the attribute are defined as parameters.

The new attribute is not added to the input layer but a new layer is generated instead.

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: any]	The input layer
Field name	FIELD_NAME	[string]	Name of the new field
Field type	FIELD_TYPE	[enumeration] Default: 0	Type of the new field. You can choose between: 0 --- Integer 1 --- Float 2 --- String
Field length	FIELD_LENGTH	[number] Default: 10	Length of the field
Field precision	FIELD_PRECISION	[number] Default: 0	Precision of the field. Useful with Float field type.
Added	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. 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.

輸出

Label	名稱	Type	說明
Added	OUTPUT	[same as input]	Vector layer with new field added

Python code

Algorithm ID: qgis:addfieldtoattributestable

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

24.1.19.3. Add unique value index field

Takes a vector layer and an attribute and adds a new numeric field.

Values in this field correspond to values in the specified attribute, so features with the same value for the attribute will have the same value in the new numeric field.

This creates a numeric equivalent of the specified attribute, which defines the same classes.

The new attribute is not added to the input layer but a new layer is generated instead.

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: any]	The input layer.
Class field	FIELD	[tablefield: any]	Features that have the same value for this field will get the same index.
Output field name	FIELD_NAME	[string] Default: 'NUM_FIELD'	Name of the new field containing the indexes.
Layer with index field	OUTPUT	[vector: any] Default: [Create temporary layer]	Vector layer with the numeric field containing indexes. One of: Skip Output Create Temporary Layer Save to File... Save to Geopackage... Save to PostGIS Table...... The file encoding can also be changed here.
Class summary	SUMMARY_OUTPUT	[table] Default: [Skip output]	Specify the table to contain the summary of the class field mapped to the corresponding unique value. One of: Skip Output Create Temporary Layer Save to File... Save to Geopackage... Save to PostGIS Table...... The file encoding can also be changed here.

輸出

Label	名稱	Type	說明
Layer with index field	OUTPUT	[same as input]	Vector layer with the numeric field containing indexes.
Class summary	SUMMARY_OUTPUT	[table] Default: [Skip Output]	Table with summary of the class field mapped to the corresponding unique value.

Python code

Algorithm ID: qgis:adduniquevalueindexfield

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

24.1.19.4. Add X/Y fields to layer

Adds X and Y (or latitude/longitude) fields to a point layer. The X/Y fields can be calculated in a different CRS to the layer (e.g. creating latitude/longitude fields for a layer in a projected CRS).

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: point]	The input layer.
Coordinate system	CRS	[crs] Default: "EPSG:4326"	Coordinate reference system to use for the generated x and y fields.
Field prefix Optional	PREFIX	[string]	Prefix to add to the new field names to avoid name collisions with fields in the input layer.
Added fields	OUTPUT	[vector: point] Default: [Create temporary layer]	Specify the output layer. One of: Create Temporary Layer Save to File... Save to Geopackage... Save to PostGIS Table... The file encoding can also be changed here.

輸出

Label	名稱	Type	說明
Added fields	OUTPUT	[vector: point]	The output layer - identical to the input layer but with two new double fields, x and y.

Python code

Algorithm ID: qgis:addxyfieldstolayer

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

24.1.19.5. Advanced Python field calculator

Adds a new attribute to a vector layer, with values resulting from applying an expression to each feature.

The expression is defined as a Python function.

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: any]	Input vector layer
Result field name	FIELD_NAME	[string] Default: 'NewField'	Name of the new field
Field type	FIELD_TYPE	[enumeration] Default: 0	Type of the new field. One of: 0 --- Integer 1 --- Float 2 --- String
Field length	FIELD_LENGTH	[number] Default: 10	Length of the field
Field precision	FIELD_PRECISION	[number] Default: 3	Precision of the field. Useful with Float field type.
Global expression Optional	GLOBAL	[string]	The code in the global expression section will be executed only once before the calculator starts iterating through all the features of the input layer. Therefore, this is the correct place to import necessary modules or to calculate variables that will be used in subsequent calculations.
Formula	FORMULA	[string]	The Python formula to evaluate. Example: To calculate the area of an input polygon layer you can add: value = $geom.area()
Calculated	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the vector layer with the new calculated field. One of: Create Temporary Layer Save to File... Save to Geopackage... Save to PostGIS Table...... The file encoding can also be changed here.

輸出

Label	名稱	Type	說明
Calculated	OUTPUT	[same as input]	Vector layer with the new calculated field

Python code

Algorithm ID: qgis:advancedpythonfieldcalculator

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

24.1.19.6. Drop field(s)

Takes a vector layer and generates a new one that has the same features but without the selected columns.

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: any]	Input vector layer to drop field(s) from
Fields to drop	COLUMN	[tablefield: any] [list]	The field(s) to drop
Remaining fields	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer with the remaining fields. One of: Create Temporary Layer Save to File... Save to Geopackage... Save to PostGIS Table...... The file encoding can also be changed here.

輸出

Label	名稱	Type	說明
Remaining fields	OUTPUT	[same as input]	Vector layer with the remaining fields

Python code

Algorithm ID: qgis:deletecolumn

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

24.1.19.7. Explode HStore Field

Creates a copy of the input layer and adds a new field for every unique key in the HStore field.

The expected field list is an optional comma separated list. If this list is specified, only these fields are added and the HStore field is updated. By default, all unique keys are added.

The PostgreSQL HStore is a simple key-value store used in PostgreSQL and OGR (when reading an OSM file with the other_tags field.

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: any]	Input vector layer
HStore field	FIELD	[tablefield: any]	The field(s) to drop
Expected list of fields separated by a comma Optional	EXPECTED_FIELDS	[string] Default: ''	Comma-separated list of fields to extract. The HStore field will be updated by removing these keys.
Exploded	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer Save to File... Save to Geopackage... Save to PostGIS Table...... The file encoding can also be changed here.

輸出

Label	名稱	Type	說明
Exploded	OUTPUT	[same as input]	Output vector layer

Python code

Algorithm ID: qgis:explodehstorefield

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

24.1.19.8. Extract binary field

Extracts contents from a binary field, saving them to individual files. Filenames can be generated using values taken from an attribute in the source table or based on a more complex expression.

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: any]	Input vector layer containing the binary data
Binary field	FIELD	[tablefield: any]	Field containing the binary data
File name	FILENAME	[expression]	Field or expression-based text to name each output file
Destination folder	FOLDER	[folder] Default: [Save to a temporary folder]	Folder in which to store the output files. One of: Save to a Temporary Directory Save to Directory... The file encoding can also be changed here.

輸出

Label	名稱	Type	說明
Folder	FOLDER	[folder]	The folder that contains the output files.

Python code

Algorithm ID: qgis:extractbinary

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

24.1.19.9. Feature filter

Filters features from the input layer and redirects them to one or several outputs. If you do not know about any attribute names that are common to all possible input layers, filtering is only possible on the feature geometry and general record mechanisms, such as $id and uuid.

备注

This algorithm is only available from the Graphical modeler.

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: any]	The input layer.
Outputs and filters (one or more)	OUTPUT_<name of the filter>	[same as input]	The output layers with filters (as many as there are filters).

輸出

Label	名稱	Type	說明
Output (one or more)	native:filter_1:OUTPUT_<name of filter>	[same as input]	The output layers with filtered features (as many as there are filters).

Python code

Algorithm ID: qgis:featurefilter

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

24.1.19.10. Field calculator

Opens the field calculator (see Expressions). You can use all the supported expressions and functions.

A new layer is created with the result of the expression.

The field calculator is very useful when used in The graphical modeler.

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: any]	The layer to calculate on
Output field name	FIELD_NAME	[string]	The name of the field for the results
Output field type	FIELD_TYPE	[enumeration] Default: 0	The type of the field. One of: 0 --- Float 1 --- Integer 2 --- String 3 --- Date
Output field width	FIELD_LENGTH	[number] Default: 10	The length of the result field (minimum 0)
Field precision	FIELD_PRECISION	[number] Default: 3	The precision of the result field (minimum 0, maximum 15)
Create new field	NEW_FIELD	[boolean] Default: True	Should the result field be a new field
Formula	FORMULA	[expression]	The formula to use to calculate the result
Output file	OUTPUT	[vector: any] Default: [Save to temporary file]	Specification of the output layer.

輸出

Label	名稱	Type	說明
Calculated	OUTPUT	[vector: any]	Output layer with the calculated field values

Python code

Algorithm ID: qgis:fieldcalculator

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

24.1.19.11. Refactor fields

Allows editing the structure of the attribute table of a vector layer.

Fields can be modified in their type and name, using a fields mapping.

The original layer is not modified. A new layer is generated, which contains a modified attribute table, according to the provided fields mapping.

Refactor layer fields allows to:

• Change field names and types

• Add and remove fields

• Reorder fields

• Calculate new fields based on expressions

• Load field list from another layer

图 24.102 Refactor fields dialog

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: any]	The layer to modify
Fields mapping	FIELDS_MAPPING	[list]	List of output fields with their definitions. The embedded table lists all the fields of the source layer and allows you to edit them: Click to create a new field. Click to remove a field. Use and to change the selected field order. Click to reset to the default view. For each of the fields you'd like to reuse, you need to fill the following options: Source expression (expression) [expression] Field or expression from the input layer. Field name (name) [string] Name of the field in the output layer. By default input field name is kept. Type (type) [enumeration] Data type of the output field. One of: Date (14) DateTime (16) Double (6) Integer (2) Integer64 (4) String (10) Boolean (1) Length (length) [number] Length of the output field. Precision (precision) [number] Precision of the output field. Fields from another layer can be loaded into the field list in Load fields from layer.
Refactored	OUTPUT	[vector: any] Default: [Create temporary layer]	Specification of the output layer. One of: Create Temporary Layer Save to File... Save to Geopackage... Save to PostGIS Table...... The file encoding can also be changed here.

輸出

Label	名稱	Type	說明
Refactored	OUTPUT	[vector: any]	Output layer with refactored fields

Python code

Algorithm ID: qgis:refactorfields

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

24.1.19.12. Rename vector field

Renames an existing field from a vector layer.

The original layer is not modified. A new layer is generated where the attribute table contains the renamed field.

参见

Refactor fields

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: any]	The input vector layer
Field to rename	FIELD	[string]	The field to be altered
New field name	NEW_NAME	[string]	The new field name
Renamed	OUTPUT	[vector: same as input] Default: [Create temporary layer]	Specification of the output layer. One of: Create Temporary Layer Save to File... Save to Geopackage... Save to PostGIS Table...... The file encoding can also be changed here.

輸出

Label	名稱	Type	說明
Renamed	OUTPUT	[vector: same as input]	Output layer with the renamed field

Python code

Algorithm ID: qgis:renametablefield

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

24.1.19.13. Text to float

Modifies the type of a given attribute in a vector layer, converting a text attribute containing numeric strings into a numeric attribute (e.g. '1' to 1.0).

The algorithm creates a new vector layer so the source one is not modified.

If the conversion is not possible the selected column will have NULL values.

參數

Label	名稱	Type	說明
Input layer	INPUT	[vector: any]	The input vector layer.
Text attribute to convert to float	FIELD	[tablefield: string]	The string field for the input layer that is to be converted to a float field.
Float from text	OUTPUT	[same as input] Default: [Create Temporary Layer]	Specify the output layer. One of: Create Temporary Layer Save to File... Save to Geopackage... Save to PostGIS Table...... The file encoding can also be changed here.

輸出

Label	名稱	Type	說明
Float from text	OUTPUT	[same as input]	Output vector layer with the string field converted into a float field

Python code

Algorithm ID: qgis:texttofloat

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.