23.1.14. Vector general

23.1.14.1. Assign projection

Assigns a new projection to a vector layer.

It creates a new layer with the exact same features and geometries as the input one, but assigned to a new CRS. The geometries are not reprojected, they are just assigned to a different CRS.

This algorithm can be used to repair layers which have been assigned an incorrect projection.

Attributes are not modified by this algorithm.

See also

Define Shapefile projection, Find projection, Reproject layer

23.1.14.1.1. Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Vector layer with wrong or missing CRS
Assigned CRS	CRS	[crs] Default: EPSG:4326 - WGS84	Select the new CRS to assign to the vector layer
Assigned CRS (Optional)	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output layer containing only the duplicates. 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.

23.1.14.1.2. Outputs

Label	Name	Type	Description
Assigned CRS	OUTPUT	[same as input]	Vector layer with assigned projection

23.1.14.1.3. Python code

Algorithm ID: qgis:assignprojection

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.

23.1.14.2. Build virtual vector

Creates a virtual vector layer that contains a set of vector layer. The output virtual vector layer will not be open in the current project.

This algorithm is especially useful in case another algorithm needs multiple layers but accept only one vrt in which the layers are specified.

23.1.14.2.1. Parameters

Label	Name	Type	Description
Input datasources	INPUT	[vector: any] [list]	Select the vector layers you want to use to build the virtual vector
Create “unioned” VRT	UNIONED	[boolean] Default: False	Check if you want to unite all the vectors in a single vrt file
Virtual vector	OUTPUT	[same as input] Default: [Save to temporary file]	Specify the output layer containing only the duplicates. One of: Save to a Temporary File Save to File… The file encoding can also be changed here.

23.1.14.2.2. Outputs

Label	Name	Type	Description
Virtual vector	OUTPUT	[vector: any]	The output virtual vector made from the chosen sources

23.1.14.3. Convert layer to spatial bookmarks

Creates spatial bookmarks corresponding to the extent of features contained in a layer.

23.1.14.3.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: line, polygon]	The input vector layer
Bookmark destination	DESTINATION	[enumeration] Default: 0	Select the destination for the bookmarks. One of: 0 — Project bookmarks 1 — User bookmarks
Name field	NAME_EXPRESSION	[expression]	Field or expression that will give names to the generated bookmarks
Group field	GROUP_EXPRESSION	[expression]	Field or expression that will provide groups for the generated bookmarks

23.1.14.3.2. Outputs

Label	Name	Type	Description
Count of bookmarks added	COUNT	[number]

23.1.14.3.3. Python code

Algorithm ID: qgis:layertobookmarks

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.

23.1.14.4. Convert spatial bookmarks to layer

Creates a new layer containing polygon features for stored spatial bookmarks. The export can be filtered to only bookmarks belonging to the current project, to all user bookmarks, or a combination of both.

23.1.14.4.1. Parameters

Label	Name	Type	Description
Bookmark source	SOURCE	[enumeration] [list] Default: [0,1]	Select the source(s) of the bookmarks. One or more of: 0 — Project bookmarks 1 — User bookmarks
Output CRS	CRS	[crs] Default: EPSG:4326 - WGS 84	The CRS of the output layer
Output	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output 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.

23.1.14.4.2. Outputs

Label	Name	Type	Description
Output	OUTPUT	[vector: polygon]	The output (bookmarks) vector layer

23.1.14.4.3. Python code

Algorithm ID: qgis:bookmarkstolayer

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.

23.1.14.5. Create attribute index

Creates an index against a field of the attribute table to speed up queries. The support for index creation depends on both the layer’s data provider and the field type.

No outputs are created: the index is stored on the layer itself.

23.1.14.5.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Select the vector layer you want to create an attribute index for
Attribute to index	FIELD	[tablefield: any]	Field of the vector layer

23.1.14.5.2. Outputs

Label	Name	Type	Description
Indexed layer	OUTPUT	[same as input]	A copy of the input vector layer with an index for the specified field

23.1.14.5.3. Python code

Algorithm ID: qgis:createattributeindex

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.

23.1.14.6. Create spatial index

Creates an index to speed up access to the features in a layer based on their spatial location. Support for spatial index creation is dependent on the layer’s data provider.

No new output layers are created.

Default menu: Vector ▶ Data Management Tools

23.1.14.6.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Input vector layer

23.1.14.6.2. Outputs

Label	Name	Type	Description
Indexed layer	OUTPUT	[same as input]	A copy of the input vector layer with a spatial index

23.1.14.6.3. Python code

Algorithm ID: qgis:createspatialindex

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.

23.1.14.7. Define Shapefile projection

Sets the CRS (projection) of an existing Shapefile format dataset to the provided CRS. It is very useful when a Shapefile format dataset is missing the prj file and you know the correct projection.

Contrary to the Assign projection algorithm, it modifies the current layer and will not output a new layer.

Note

For Shapefile datasets, the .prj and .qpj files will be overwritten - or created if missing - to match the provided CRS.

Default menu: Vector ▶ Data Management Tools

See also

Assign projection, Find projection, Reproject layer

23.1.14.7.1. Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Vector layer with missing projection information
CRS	CRS	[crs]	Select the CRS to assign to the vector layer

23.1.14.7.2. Outputs

Label	Name	Type	Description
	INPUT	[same as input]	The input vector layer with the defined projection

23.1.14.7.3. Python code

Algorithm ID: qgis:definecurrentprojection

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.

23.1.14.8. Delete duplicate geometries

Finds and removes duplicated geometries.

Attributes are not checked, so in case two features have identical geometries but different attributes, only one of them will be added to the result layer.

See also

Remove null geometries, Delete duplicates by attribute

23.1.14.8.1. Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	The layer with duplicate geometries you want to clean
Cleaned	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output 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.

23.1.14.8.2. Outputs

Label	Name	Type	Description
Count of discarded duplicate records	DUPLICATE_COUNT	[number]	Count of discarded duplicate records
Cleaned	OUTPUT	[same as input]	The output layer without any duplicated geometries
Count of retained records	RETAINED_COUNT	[number]	Count of unique records

23.1.14.8.3. Python code

Algorithm ID: qgis:deleteduplicategeometries

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.

23.1.14.9. Delete duplicates by attribute

Deletes duplicate rows by only considering the specified field / fields. The first matching row will be retained, and duplicates will be discarded.

Optionally, these duplicate records can be saved to a separate output for analysis.

See also

Delete duplicate geometries

23.1.14.9.1. Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	The input layer
Fields to match duplicates by	FIELDS	[tablefield: any] [list]	Fields defining duplicates. Features with identical values for all these fields are considered duplicates.
Filtered (no duplicates)	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output layer containing the unique 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.
Filtered (duplicates) (Optional)	DUPLICATES	[same as input] Default: [Skip output]	Specify the output layer containing only the duplicates. One of: Skip output Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

23.1.14.9.2. Outputs

Label	Name	Type	Description
Filtered (duplicates) Optional	DUPLICATES	[same as input] Default: [Skip output]	Vector layer containing the removed features. Will not be produced if not specified (left as [Skip output]).
Count of discarded duplicate records	DUPLICATE_COUNT	[number]	Count of discarded duplicate records
Filtered (no duplicates)	OUTPUT	[same as input]	Vector layer containing the unique features.
Count of retained records	RETAINED_COUNT	[number]	Count of unique records

23.1.14.9.3. Python code

Algorithm ID: qgis:deleteduplicatesbyattribute

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.

23.1.14.10. Drop geometries

Creates a simple geometryless copy of the input layer attribute table. It keeps the attribute table of the source layer.

If the file is saved in a local folder, you can choose between many file formats.

Allows features in-place modification

See also

Delete duplicate geometries, Remove null geometries

23.1.14.10.1. Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	The input vector layer
Dropped geometries	OUTPUT	[table]	Specify the output geometryless 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.

23.1.14.10.2. Outputs

Label	Name	Type	Description
Dropped geometries	OUTPUT	[table]	The output geometryless layer. A copy of the original attribute table.

23.1.14.10.3. Python code

Algorithm ID: qgis:dropgeometries

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.

23.1.14.11. Execute SQL

Runs a simple or complex query with SQL syntax on the source layer.

Input datasources are identified with input1, input2… inputN and a simple query will look like SELECT * FROM input1.

Beside a simple query, you can add expressions or variables within the SQL query parameter itself. This is particulary useful if this algorithm is executed within a Processing model and you want to use a model input as a parameter of the query. An example of a query will then be SELECT * FROM [% @table %] where @table is the variable that identifies the model input.

The result of the query will be added as a new layer.

See also

SpatiaLite execute SQL, PostgreSQL execute SQL

23.1.14.11.1. Parameters

Label	Name	Type	Description
Additional input datasources (called input1, .., inputN in the query)	INPUT_DATASOURCES	[vector: any] [list]	List of layers to query. In the SQL editor you can refer these layers with their real name or also with input1, input2, inputN depending on how many layers have been chosen.
SQL query	INPUT_QUERY	[string]	Type the string of your SQL query, e.g. SELECT * FROM input1.
Unique identifier field Optional	INPUT_UID_FIELD	[string]	Specify the column with unique ID
Geometry field Optional	INPUT_GEOMETRY_FIELD	[string]	Specify the geometry field
Geometry type Optional	INPUT_GEOMETRY_TYPE	[enumeration] Default: 0	Choose the geometry of the result. By default the algorithm will autodetect it. One of: 0 — Autodetect 1 — No geometry 2 — Point 3 — LineString 4 — Polygon 5 — MultiPoint 6 — MultiLineString 7 — MultiPolygon
CRS Optional	INPUT_GEOMETRY_CRS	[crs]	The CRS to assign to the output layer
SQL Output	OUTPUT	[vector: any] Default: [Create temporary layer]	Specify the output layer created by the query. 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.

23.1.14.11.2. Outputs

Label	Name	Type	Description
SQL Output	OUTPUT	[vector: any]	Vector layer created by the query

23.1.14.11.3. Python code

Algorithm ID: qgis:executesql

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.

23.1.14.12. Extract selected features

Saves the selected features as a new layer.

Note

If the selected layer has no selected features, the newly created layer will be empty.

23.1.14.12.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Layer to save the selection from
Selected features	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the vector layer for the 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.

23.1.14.12.2. Outputs

Label	Name	Type	Description
Selected features	OUTPUT	[same as input]	Vector layer with only the selected features, or no feature if none was selected.

23.1.14.12.3. Python code

Algorithm ID: qgis:saveselectedfeatures

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.

23.1.14.13. Find projection

Creates a shortlist of candidate coordinate reference systems, for instance for a layer with an unknown projection.

The area that the layer is expected to cover must be specified via the target area parameter. The coordinate reference system for this target area must be known to QGIS.

The algorithm operates by testing the layer’s extent in every known reference system and then listing any for which the bounds would be near the target area if the layer was in this projection.

See also

Assign projection, Define Shapefile projection, Reproject layer

23.1.14.13.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Layer with unknown projection
Target area for layer (xmin, xmax, ymin, ymax)	TARGET_AREA	[extent]	The area that the layer covers. The options for specifying the extent are: Use Canvas Extent Select Extent on Canvas Use Layer Extent It is also possible to provide the extent coordinates directly (xmin, xmax, ymin, ymax).
CRS candidates	OUTPUT	[table] Default: [Create temporary layer]	Specify the table (geometryless layer) for the CRS suggestions (EPSG codes). 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.

23.1.14.13.2. Outputs

Label	Name	Type	Description
CRS candidates	OUTPUT	[table]	A table with all the CRS (EPSG codes) of the matching criteria.

23.1.14.13.3. Python code

Algorithm ID: qgis:findprojection

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.

23.1.14.14. Join attributes by field value

Takes an input vector layer and creates a new vector layer that is an extended version of the input one, with additional attributes in its attribute table.

The additional attributes and their values are taken from a second vector layer. An attribute is selected in each of them to define the join criteria.

See also

Join attributes by nearest, Join attributes by location

23.1.14.14.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Input vector layer. The output layer will consist of the features of this layer with attributes from matching features in the second layer.
Table field	FIELD	[tablefield: any]	Field of the source layer to use for the join
Input layer 2	INPUT_2	[vector: any]	Layer with the attribute table to join
Table field 2	FIELD_2	[tablefield: any]	Field of the second (join) layer to use for the join The type of the field must be equal to (or compatible with) the input table field type.
Layer 2 fields to copy Optional	FIELDS_TO_COPY	[tablefield: any] [list]	Select the specific fields you want to add. By default all the fields are added.
Join type	METHOD	[enumeration] Default: 1	The type of the final joined layer. One of: 0 — Create separate feature for each matching feature (one-to-many) 1 — Take attributes of the first matching feature only (one-to-one)
Discard records which could not be joined	DISCARD_NONMATCHING	[boolean] Default: True	Check if you don’t want to keep the features that could not be joined
Joined field prefix Optional	PREFIX	[string]	Add a prefix to joined fields in order to easily identify them and avoid field name collision
Joined layer	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer for the join. 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.
Unjoinable features from first layer	NON_MATCHING	[same as input] Default: [Skip output]	Specify the output vector layer for unjoinable features from first layer. One of: Skip output Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

23.1.14.14.2. Outputs

Label	Name	Type	Description
Number of joined features from input table	JOINED_COUNT	[number]
Unjoinable features from first layer Optional	NON_MATCHING	[same as input]	Vector layer with the non-matched features
Joined layer	OUTPUT	[same as input]	Output vector layer with added attributes from the join
Number of unjoinable features from input table Optional	UNJOINABLE_COUNT	[number]

23.1.14.14.3. Python code

Algorithm ID: qgis:joinattributestable

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.

23.1.14.15. Join attributes by location

Takes an input vector layer and creates a new vector layer that is an extended version of the input one, with additional attributes in its attribute table.

The additional attributes and their values are taken from a second vector layer. A spatial criteria is applied to select the values from the second layer that are added to each feature from the first layer.

Default menu: Vector ▶ Data Management Tools

See also

Join attributes by nearest, Join attributes by field value, Join attributes by location (summary)

23.1.14.15.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Input vector layer. The output layer will consist of the features of this layer with attributes from matching features in the second layer.
Join layer	JOIN	[vector: any]	The attributes of this vector layer will be added to the source layer attribute table.
Geometric predicate	PREDICATE	[enumeration] [list] Default: [0]	Select the geometric criteria. One or more of: 0 — intersects 1 — contains 2 — equals 3 — touches 4 — overlaps 5 — within 6 — crosses
Fields to add (leave empty to use all fields) Optional	JOIN_FIELDS	[tablefield: any] [list]	Select the specific fields you want to add. By default all the fields are added.
Join type	METHOD	[enumeration]	The type of the final joined layer. One of: 0 — Create separate feature for each matching feature (one-to-many) 1 — Take attributes of the first matching feature only (one-to-one)
Discard records which could not be joined	DISCARD_NONMATCHING	[boolean] Default: False	Remove from the output the input layer records which could not be joined
Joined field prefix Optional	PREFIX	[string]	Add a prefix to joined fields in order to easily identify them and avoid field name collision
Joined layer	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer for the join. 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.
Unjoinable features from first layer	NON_MATCHING	[same as input] Default: [Skip output]	Specify the output vector layer for unjoinable features from first layer. One of: Skip output Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

23.1.14.15.2. Outputs

Label	Name	Type	Description
Number of joined features from input table	JOINED_COUNT	[number]
Unjoinable features from first layer Optional	NON_MATCHING	[same as input]	Vector layer of the non-matched features
Joined layer	OUTPUT	[same as input]	Output vector layer with added attributes from the join

23.1.14.15.3. Python code

Algorithm ID: qgis:joinattributesbylocation

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.

23.1.14.16. Join attributes by location (summary)

Takes an input vector layer and creates a new vector layer that is an extended version of the input one, with additional attributes in its attribute table.

The additional attributes and their values are taken from a second vector layer. A spatial criteria is applied to select the values from the second layer that are added to each feature from the first layer.

The algorithm calculates a statistical summary for the values from matching features in the second layer (e.g. maximum value, mean value, etc).

See also

Join attributes by location

23.1.14.16.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Input vector layer. The output layer will consist of the features of this layer with attributes from matching features in the second layer.
Join layer	JOIN	[vector: any]	The attributes of this vector layer will be added to the source layer attribute table.
Geometric predicate	PREDICATE	[enumeration] [list] Default: [0]	Select the geometric criteria. One or more of: 0 — intersects 1 — contains 2 — equals 3 — touches 4 — overlaps 5 — within 6 — crosses
Fields to summarize (leave empty to use all fields) Optional	JOIN_FIELDS	[tablefield: any] [list]	Select the specific fields you want to add and summarize. By default all the fields are added.
Summaries to calculate (leave empty to use all fields) Optional	SUMMARIES	[enumeration] [list] Default: []	Choose which type of summary you want to add to each field and for each feature. One or more of: 0 — count 1 — unique 2 — min 3 — max 4 — range 5 — sum 6 — mean 7 — median 8 — stddev 9 — minority 10 — majority 11 — q1 12 — q3 13 — iqr 14 — empty 15 — filled 16 — min_length 17 — max_length 18 — mean_length
Discard records which could not be joined	DISCARD_NONMATCHING	[boolean] Default: False	Remove from the output the input layer records which could not be joined
Joined layer	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer for the join. 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.

23.1.14.16.2. Outputs

Label	Name	Type	Description
Joined layer	OUTPUT	[same as input]	Output vector layer with summarized attributes from the join

23.1.14.16.3. Python code

Algorithm ID: qgis:joinbylocationsummary

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.

23.1.14.17. Join attributes by nearest

Takes an input vector layer and creates a new vector layer with additional fields in its attribute table. The additional attributes and their values are taken from a second vector layer. Features are joined by finding the closest features from each layer.

By default only the nearest feature is joined, but the join can also join to the k-nearest neighboring features.

If a maximum distance is specified, only features which are closer than this distance will be matched.

See also

Nearest neighbour analysis, Join attributes by field value, Join attributes by location, Distance matrix

23.1.14.17.1. Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	The input layer.
Input layer 2	INPUT_2	[vector: any]	The join layer.
Layer 2 fields to copy (leave empty to copy all fields)	FIELDS_TO_COPY	[fields]	Join layer fields to copy (if empty, all fields will be copied).
Discard records which could not be joined	DISCARD_NONMATCHING	[boolean] Default: False	Remove from the output the input layer records which could not be joined
Joined field prefix	PREFIX	[string]	Joined field prefix
Maximum nearest neighbors	NEIGHBORS	[number] Default: 1	Maximum number of nearest neighbors
Maximum distance	MAX_DISTANCE	[number]	Maximum search distance
Joined layer	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the vector layer containing the joined 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.
Unjoinable features from first layer	NON_MATCHING	[same as input] Default: [Skip output]	Specify the vector layer containing the features that could not be joined. One of: Skip output Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

23.1.14.17.2. Outputs

Label	Name	Type	Description
Joined layer	OUTPUT	[same as input]	The output joined layer.
Unjoinable features from first layer	NON_MATCHING	[same as input]	Layer containing the features from first layer that could not be joined to any features in the join layer.
Number of joined features from input table	JOINED_COUNT	[number]	Number of features from the input table that have been joined.
Number of unjoinable features from input table	UNJOINABLE_COUNT	[number]	Number of features from the input table that could not be joined.

23.1.14.17.3. Python code

Algorithm ID: qgis:joinbynearest

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.

23.1.14.18. Merge vector layers

Combines multiple vector layers of the same geometry type into a single one.

If attributes tables are different, the attribute table of the resulting layer will contain the attributes from all input layers. Non-matching fields will be appended at the end of the attribute table.

If any input layers contain Z or M values, then the output layer will also contain these values. Similarly, if any of the input layers are multi-part, the output layer will also be a multi-part layer.

Optionally, the destination coordinate reference system (CRS) for the merged layer can be set. If it is not set, the CRS will be taken from the first input layer. All layers will be reprojected to match this CRS.

Default menu: Vector ▶ Data Management Tools

See also

Split vector layer

23.1.14.18.1. Parameters

Label	Name	Type	Description
Input Layers	LAYERS	[vector: any] [list]	The layers that are to be merged into a single layer. Layers should be of the same geometry type.
Destination CRS Optional	CRS	[crs]	Choose the CRS for the output layer. If not specified, the CRS of the first input layer is used.
Merged	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.

23.1.14.18.2. Outputs

Label	Name	Type	Description
Merged	OUTPUT	[same as input]	Output vector layer containing all the features and attributes from the input layers.

23.1.14.18.3. Python code

Algorithm ID: qgis:mergevectorlayers

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.

23.1.14.19. Order by expression

Sorts a vector layer according to an expression: changes the feature index according to an expression.

Be careful, it might not work as expected with some providers, the order might not be kept every time.

23.1.14.19.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Input vector layer to sort
Expression	EXPRESSION	[expression]	Expression to use for the sorting
Sort ascending	ASCENDING	[boolean] Default: True	If checked the vector layer will be sorted from small to large values.
Sort nulls first	NULLS_FIRST	[boolean] Default: False	If checked, Null values are placed first
Ordered	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.

23.1.14.19.2. Outputs

Label	Name	Type	Description
Ordered	OUTPUT	[same as input]	Output (sorted) vector layer

23.1.14.19.3. Python code

Algorithm ID: qgis:orderbyexpression

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.

23.1.14.20. Reproject layer

Reprojects a vector layer in a different CRS. The reprojected layer will have the same features and attributes of the input layer.

Allows features in-place modification

See also

Assign projection, Define Shapefile projection, Find projection

23.1.14.20.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Input vector layer to reproject
Target CRS	TARGET_CRS	[crs] Default: EPSG:4326 - WGS 84	Destination coordinate reference system
Reprojected	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.

23.1.14.20.2. Outputs

Label	Name	Type	Description
Reprojected	OUTPUT	[same as input]	Output (reprojected) vector layer

23.1.14.20.3. Python code

Algorithm ID: qgis:reprojectlayer

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.

23.1.14.21. Set style for vector layer

Sets the style of a vector layer. The style must be defined in a QML file.

No new output are created: the style is immediately assigned to the vector layer.

See also

Set style for raster layer

23.1.14.21.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Input vector layer you want to set the style for
Style file	STYLE	[file]	qml file of the style

23.1.14.21.2. Outputs

Label	Name	Type	Description
Input Layer	INPUT	[same as input]	The input vector layer with the new style

23.1.14.21.3. Python code

Algorithm ID: qgis:setstyleforvectorlayer

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.

23.1.14.22. Split features by character

Features are split into multiple output features by splitting a field’s value at a specified character. For instance, if a layer contains features with multiple comma separated values contained in a single field, this algorithm can be used to split these values up across multiple output features. Geometries and other attributes remain unchanged in the output. Optionally, the separator string can be a regular expression for added flexibility.

23.1.14.22.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Input vector layer
Split using values in the field	FIELD	[tablefield: any]	Field to use for splitting
Split value using character	CHAR	[string]	Character to use for splitting
Use regular expression separator	REGEX	[boolean] Default: False
Split	OUTPUT	[same as input] Default: Create temporary layer	Specify 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.

23.1.14.22.2. Outputs

Label	Name	Type	Description
Split	OUTPUT	[same as input]	The output vector layer.

23.1.14.22.3. Python code

Algorithm ID: qgis:splitfeaturesbycharacter

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.

23.1.14.23. Split vector layer

Creates a set of vectors in an output folder based on an input layer and an attribute. The output folder will contain as many layers as the unique values found in the desired field.

The number of files generated is equal to the number of different values found for the specified attribute.

It is the opposite operation of merging.

Default menu: Vector ▶ Data Management Tools

See also

Merge vector layers

23.1.14.23.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Input vector layer
Unique ID field	FIELD	[tablefield: any]	Field to use for splitting
Output directory	OUTPUT	[folder] Default: [Save to temporary folder]	Specify the directory for the output layers. One of: Save to a Temporary Directory Save to Directory… The file encoding can also be changed here.

23.1.14.23.2. Outputs

Label	Name	Type	Description
Output directory	OUTPUT	[folder]	The directory for the output layers
Output layers	OUTPUT_LAYERS	[same as input] [list]	The output vector layers resulting from the split.

23.1.14.23.3. Python code

Algorithm ID: qgis:splitvectorlayer

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.

23.1.14.24. Truncate table

Truncates a layer, by deleting all features from within the layer.

Warning

This algorithm modifies the layer in place, and deleted features cannot be restored!

23.1.14.24.1. Parameters

Label	Name	Type	Description
Input Layer	INPUT	[vector: any]	Input vector layer

23.1.14.24.2. Outputs

Label	Name	Type	Description
Truncated layer	OUTPUT	[folder]	The truncated (empty) layer

23.1.14.24.3. Python code

Algorithm ID: qgis:truncatetable

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.