Docs for ‘QGIS testing’. Visit http://docs.qgis.org/2.18 for QGIS 2.18 docs and translations.

Vector geometry

Boundary

Description

Returns the closure of the combinatorial boundary of the input geometries (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. Only valid for polygon or line layers.

Parameters

Input layer [vector: line, polygon]
Source layer to use.

Output

Output layer [vector: point, line]
Boundary from the input layer (point for line, and line for polygon).

Console usage

processing.runalg('qgis:boundary', input_layer, output_layer)

See also

Bounding boxes

Description

This algorithm calculates the bounding box (envelope) of each feature in an input layer.

Parameters

Input layer [vector: any]
Source layer to check.

Outputs

output_layer [vector: polygon]
Output bounding boxes from input layer.

Console usage

processing.runalg('qgis:boundingboxes', input_layer, output_layer)

See also

Check validity

Description

Check features geometry validity.

Parameters

Input layer [vector: any]
Source layer to check.
Method [selection]

Check validity method.

Options:

  • 0 — The one selected in digitizing settings
  • 1 — QGIS
  • 2 — GEOS

Default: 0

Outputs

Valid output [vector]
Output valid features, unchanged.
Invalid output [vector]
Output invalid features, with an additional _errors field describing the validity problems.
Error output [vector]
Output exact position on the validity problems as a point layer with a message field.

Console usage

processing.runalg('qgis:checkvalidity', input_layer, method, valid_output, invalid_output, error_output)

See also

Concave hull

Description

<put algorithm description here>

Parameters

Input point layer [vector: point]
<put parameter description here>
Threshold (0-1, where 1 is equivalent with Convex Hull) [number]

<put parameter description here>

Default: 0.3

Allow holes [boolean]

<put parameter description here>

Default: True

Split multipart geometry into singleparts geometries [boolean]

<put parameter description here>

Default: False

Outputs

Concave hull [vector]
<put output description here>

Console usage

processing.runalg('qgis:concavehull', input, alpha, holes, no_multigeometry, output)

See also

Convert geometry type

Description

Converts a geometry type to another one.

Parameters

Input layer [vector: any]
Layer in input.
New geometry type [selection]

Type of conversion to perform.

Options:

  • 0 — Centroids
  • 1 — Nodes
  • 2 — Linestrings
  • 3 — Multilinestrings
  • 4 — Polygons

Default: 0

Outputs

Output [vector]
The resulting layer.

Console usage

processing.runalg('qgis:convertgeometrytype', input, type, output)

See also

Convex hull

Description

<put algorithm description here>

Parameters

Input layer [vector: any]
<put parameter description here>
Field (optional, only used if creating convex hulls by classes) [tablefield: any]

Optional.

<put parameter description here>

Method [selection]

<put parameter description here>

Options:

  • 0 — Create single minimum convex hull
  • 1 — Create convex hulls based on field

Default: 0

Outputs

Convex hull [vector]
<put output description here>

Console usage

processing.runalg('qgis:convexhull', input, field, method, output)

See also

Create points along lines

Description

<put algorithm description here>

Parameters

lines [vector: any]
<put parameter description here>
distance [number]

<put parameter description here>

Default: 1

startpoint [number]

<put parameter description here>

Default: 0

endpoint [number]

<put parameter description here>

Default: 0

Outputs

output [vector]
<put output description here>

Console usage

processing.runalg('qgis:createpointsalonglines', lines, distance, startpoint, endpoint, output)

See also

Delaunay triangulation

Description

<put algorithm description here>

Parameters

Input layer [vector: point]
<put parameter description here>

Outputs

Delaunay triangulation [vector]
<put output description here>

Console usage

processing.runalg('qgis:delaunaytriangulation', input, output)

See also

Densify geometries given an interval

Description

<put algorithm description here>

Parameters

Input layer [vector: polygon, line]
<put parameter description here>
Interval between Vertices to add [number]

<put parameter description here>

Default: 1.0

Outputs

Densified layer [vector]
<put output description here>

Console usage

processing.runalg('qgis:densifygeometriesgivenaninterval', input, interval, output)

See also

Densify geometries

Description

<put algorithm description here>

Parameters

Input layer [vector: polygon, line]
<put parameter description here>
Vertices to add [number]

<put parameter description here>

Default: 1

Outputs

Densified layer [vector]
<put output description here>

Console usage

processing.runalg('qgis:densifygeometries', input, vertices, output)

See also

Dissolve

Description

This algorithm takes a polygon or line vector layer and combines their geometries into new geometries. One or more attributes can be specified to dissolve only geometries belonging to the same class (having the same value for the specified attributes), alternatively all geometries can be dissolved.

If the geometries to be dissolved are spatially separated from each other the output will be multi geometries. In case the input is a polygon layer, common boundaries of adjacent polygons being dissolved will get erased.

Parameters

Input layer [vector: polygon, line]
Line or polygon layer to be dissolved.
Dissolve all (do not use field) [boolean]

Dissolve all geometries; values in the output layer’s fields are the ones of the first input feature that happens to be processed. Returns one feature whose geometry represents all geometries of the input layer.

Default: True

Unique ID fields [tablefield: any]

Optional.

If features share a common value in all selected field(s) their geometries will be combined. Values in the output layer’s fields are the ones of the first input feature that happens to be processed. Returns one feature for each unique value in the field. The feature’s geometry represents all input geometries with this value.

Outputs

Dissolved [vector]
output layer, either (multi) line or (multi) polygon

Console usage

processing.runalg('qgis:dissolve', input, dissolve_all, field, output)

See also

Eliminate sliver polygons

Description

This algorithm combines selected polygons of the input layer with certain adjacent polygons by erasing their common boundary. Eliminate can either use an existing selection or a logical query based on one of the layer’s fields to make the selection itself. The adjacent polygon can be either the one with the largest or smallest area or the one sharing the largest common boundary with the polygon to be eliminated. Eliminate is normally used to get rid of sliver polygons, i.e. tiny polygons that are a result of polygon intersection processes where boundaries of the inputs are similar but not identical.

Parameters

Input layer [vector: polygon]
Polygon layer in which polygons should be eliminated.
Use current selection in input layer (works only if called from toolbox) [boolean]

Check this if you want the currently selected polygons to be eliminated.

Default: False

Selection attribute [tablefield: any]
Field to be used for the logical selection.
Comparison [selection]

Comparison parameter to be used for the logical selection.

Options:

  • 0 — ==
  • 1 — !=
  • 2 — >
  • 3 — >=
  • 4 — <
  • 5 — <=
  • 6 — begins with
  • 7 — contains

Default: 0

Value [string]

Value to be used for the logical selection.

Default: 0

Merge selection with the neighbouring polygon with the [selection]

Determines which adjacent polygon the polygon to be eliminated will be combined with.

Options:

  • 0 — Largest area
  • 1 — Smallest Area
  • 2 — Largest common boundary

Default: 0

Outputs

Cleaned layer [vector]
output layer

Console usage

processing.runalg('qgis:eliminatesliverpolygons', input, keepselection, attribute, comparison, comparisonvalue, mode, output)

See also

Explode lines

Description

<put algorithm description here>

Parameters

Input layer [vector: line]
<put parameter description here>

Outputs

Output layer [vector]
<put output description here>

Console usage

processing.runalg('qgis:explodelines', input, output)

See also

Extract nodes

Description

<put algorithm description here>

Parameters

Input layer [vector: polygon, line]
<put parameter description here>

Outputs

Output layer [vector]
<put output description here>

Console usage

processing.runalg('qgis:extractnodes', input, output)

See also

Fill holes

Description

<put algorithm description here>

Parameters

Polygons [vector: any]
<put parameter description here>
Max area [number]

<put parameter description here>

Default: 100000

Outputs

Results [vector]
<put output description here>

Console usage

processing.runalg('qgis:fillholes', polygons, max_area, results)

See also

Fixed distance buffer

Description

<put algorithm description here>

Parameters

Input layer [vector: any]
<put parameter description here>
Distance [number]

<put parameter description here>

Default: 10.0

Segments [number]

<put parameter description here>

Default: 5

Dissolve result [boolean]

<put parameter description here>

Default: False

Outputs

Buffer [vector]
<put output description here>

Console usage

processing.runalg('qgis:fixeddistancebuffer', input, distance, segments, dissolve, output)

See also

Keep n biggest parts

Description

<put algorithm description here>

Parameters

Polygons [vector: polygon]
<put parameter description here>
To keep [number]

<put parameter description here>

Default: 1

Outputs

Results [vector]
<put output description here>

Console usage

processing.runalg('qgis:keepnbiggestparts', polygons, to_keep, results)

See also

Lines to polygons

Description

<put algorithm description here>

Parameters

Input layer [vector: line]
<put parameter description here>

Outputs

Output layer [vector]
<put output description here>

Console usage

processing.runalg('qgis:linestopolygons', input, output)

See also

Merge lines

Description

This algorithm joins all connected parts of MultiLineString geometries into single LineString geometries.

If any parts of the input MultiLineString geometries are not connected, the resultant geometry will be a MultiLineString containing any lines which could be merged and any non-connected line parts.

Parameters

Input layer [vector: line]
input layer (line) to merge

Outputs

Output layer [vector: line]
Resultant layer with merged line

Console usage

processing.runalg('qgis:mergelines', input, output)

See also

Multipart to singleparts

Description

<put algorithm description here>

Parameters

Input layer [vector: any]
<put parameter description here>

Outputs

Output layer [vector]
<put output description here>

Console usage

processing.runalg('qgis:multiparttosingleparts', input, output)

See also

Point on surface

Description

Returns a point guaranteed to lay on the surface of a polygon geometry.

Parameters

Input layer [vector: polygon]
Layer with polygon

Outputs

Output layer [vector: point]
The resulting layer with point on surface

Console usage

processing.runalg('qgis:pointonsurface', input, output)

See also

Points displacement

Description

Moves overlapped points at small distance, that they all become visible. The result is very similar to the output of the “Point displacement” renderer but it is permanent.

Parameters

Input layer [vector: point]
Layer with overlapped points.
Displacement distance [number]

Desired displacement distance NOTE: displacement distance should be in same units as layer.

Default: 0.00015

Horizontal distribution for two point case [boolean]

Controls distribution direction in case of two overlapped points. If True points will be distributed horizontally, otherwise they will be distributed vertically.

Default: True

Outputs

Output layer [vector]
The resulting layer with shifted overlapped points.

Console usage

processing.runalg('qgis:pointsdisplacement', input_layer, distance, horizontal, output_layer)

See also

Polygon centroids

Description

<put algorithm description here>

Parameters

Input layer [vector: polygon]
<put parameter description here>

Outputs

Output layer [vector]
<put output description here>

Console usage

processing.runalg('qgis:polygoncentroids', input_layer, output_layer)

See also

Polygonize

Description

<put algorithm description here>

Parameters

Input layer [vector: line]
<put parameter description here>
Keep table structure of line layer [boolean]

<put parameter description here>

Default: False

Create geometry columns [boolean]

<put parameter description here>

Default: True

Outputs

Output layer [vector]
<put output description here>

Console usage

processing.runalg('qgis:polygonize', input, fields, geometry, output)

See also

Polygons to lines

Description

<put algorithm description here>

Parameters

Input layer [vector: polygon]
<put parameter description here>

Outputs

Output layer [vector]
<put output description here>

Console usage

processing.runalg('qgis:polygonstolines', input, output)

See also

Simplify geometries

Description

<put algorithm description here>

Parameters

Input layer [vector: polygon, line]
<put parameter description here>
Tolerance [number]

<put parameter description here>

Default: 1.0

Outputs

Simplified layer [vector]
<put output description here>

Console usage

processing.runalg('qgis:simplifygeometries', input, tolerance, output)

See also

Singleparts to multipart

Description

<put algorithm description here>

Parameters

Input layer [vector: any]
<put parameter description here>
Unique ID field [tablefield: any]
<put parameter description here>

Outputs

Output layer [vector]
<put output description here>

Console usage

processing.runalg('qgis:singlepartstomultipart', input, field, output)

See also

Variable distance buffer

Description

<put algorithm description here>

Parameters

Input layer [vector: any]
<put parameter description here>
Distance field [tablefield: any]
<put parameter description here>
Segments [number]

<put parameter description here>

Default: 5

Dissolve result [boolean]

<put parameter description here>

Default: False

Outputs

Buffer [vector]
<put output description here>

Console usage

processing.runalg('qgis:variabledistancebuffer', input, field, segments, dissolve, output)

See also

Voronoi polygons

Description

<put algorithm description here>

Parameters

Input layer [vector: point]
<put parameter description here>
Buffer region [number]

<put parameter description here>

Default: 0.0

Outputs

Voronoi polygons [vector]
<put output description here>

Console usage

processing.runalg('qgis:voronoipolygons', input, buffer, output)

See also