Questions tagged [qgis-processing]
Spatial data processing framework that brings advanced analysis capabilities to QGIS.
1,526
questions
2
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QGIS does not load Processing algorithm's (raster) output
I wrote a simple QGIS Processing algorithm:
from qgis.core import QgsProcessing
from qgis.processing import alg
import processing
@alg(name="test", label=alg.tr("test"), group=&...
- 9,877
1
vote
1
answer
20
views
Child algorithm in custom Processing algorithm fails to find temporary output of previous child algorithm
I wrote a simple custom QGIS Processing algorithm in Python:
from qgis.core import QgsProcessing
from qgis.processing import alg
import processing
@alg(name="test", label=alg.tr("test&...
- 9,877
4
votes
1
answer
41
views
For QGIS processing algorithm python scripts, how to limit selectable layers in algorithm input when using @alg decorators
When using the @alg decorator to scaffold a processing algorithm, we use the @alg.input to declare new widgets for the interface. We can declare these as alg.SOURCE for layers we use in the algorithm.
...
- 209
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0
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19
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Create a regression model from a mixture of polygon, line and point data [closed]
I've decided for a school project that I will use a regression analysis to predict the location of new shops (dependent variable) based on a number of independent variables. I have point files for the ...
- 9
1
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0
answers
33
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Group by multiple columns in QGIS array
I'm looking to create a figure with multiple rule-based symbologies. A graduated range within a category within a main category.
The only way I think that's possible is by adding categories, ranges to ...
- 11
2
votes
1
answer
34
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QGIS Modeler - cannot use aggregate function in this context?
I am using QGIS 3.22 and
I am making some algorithm in Modeler
I am using Vector Layer as layer and Vector Field as field (it is field with real values and nulls). I want to add column with sum of ...
1
vote
0
answers
20
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QGIS model designer, get output value
I am developing a model, will go through different steps of calculation to create new field using @field calculator algorithm which can generate a layer as output.
.
One of my calculations is to ...
- 111
0
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0
answers
21
views
CSV location code decoder
Is the a way reverse a CSV cell code that was generated from PyQGIS? This is for a location point.
The code is
0101000020E6100000C5DC58CD04F65BC0CC755D611AB54040
-1
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0
answers
32
views
Filling polygon with rectangles / boxes
How can I fill a polygon with X/Y rectangle polygons up to a given maximum area size?
Maximum size given as otherwise the number of resulting boxes will be infinite along the edges of course.
For ...
- 71
1
vote
1
answer
44
views
Adding script to the Processing Toolbox in QGIS
I have a script and I would like to add it to the processing toolbox via Add Script to Toolbox using the Python icon. I received this error and I could not add my script to the processing toolbox.
The ...
- 75
0
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0
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37
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QGIS Python name 'processing' is not defined
Some time ago, I did the following script for retrieving vegetation indices from raster images. Apparently, the new Python version is not allowing running the script. The script is made to have a QGIS ...
- 487
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0
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30
views
Expression syntax using processing.run algorithms in PyQGIS
I am trying to run "Extract by expression" in a QGIS script using processing.run
layer1 = points.shp
processing.run(
'qgis:extractbyexpression',
{
'EXPRESSION': "...
0
votes
0
answers
13
views
QgsRasterCalculator doesn't allow me to perform more actions in QGIS after run it
I am trying to use QgsRasterCalculator for a simple equation:
co = mo * 0.58
This is the code:
# -*- coding: iso-8859-15 -*-
import processing
import os
from qgis.core import *
GUIEnabled = ...
- 11
0
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0
answers
41
views
How to merge selected polygons with all adjacent polygons individually?
I have a vector layer with polygons representing administrative districts of germany. For every polygon smaller than 500 km² I would like to create bigger polygons by merging each of the small ...
- 13
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0
answers
28
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How to specify GDAL driver to use for Processing INPUT?
How can I specify a specific driver to be used by GDAL/OGR when running a tool via Processing? GDAL/OGR calls them prefixes to the connection string, e.g. https://gdal.org/drivers/vector/gmlas.html#...
- 9,877
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1
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97
views
PyQGIS, custom processing algorithm: How to use selected features only?
I want to create a custom processing algorithm with PyQGIS, which is able to take a vector layer as input (in this case of type point) and then do something with it's features. It's working well as ...
- 19
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0
answers
22
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Error in LAERS parameter in processing.run in qgis3.28 while writing standalone python script
I am trying to download google satellite images in ".tif" form by qgis3.28 My code is as following
import requests
from qgis.core import QgsApplication, QgsRasterLayer, QgsMapLayer
from qgis ...
3
votes
2
answers
183
views
Generating points along the line at equal intervals excluding vertices in QGIS
I want to generate points along a line at equal intervals but the final point layer should not contain the vertices points. It should only contain points at specified intervals.
Tools in QGIS such as &...
- 31
0
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0
answers
63
views
Unable to run SAGA-Terrain Analysis-Fill sinks (wang&liu)
I am trying to do a Watershed analysis using QGIS. However if I want to run the SAGA function Fill sinks (Wang & Liu) I get an error that the 3 files were not created (full error down below). I ...
- 1
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votes
1
answer
60
views
Select Polygons in layer A with a specific geolocation criteria in relation to each other and layer B
I am trying to select Polygons from Layer A with the following rules:
Polygon in Layer A is smaller than 1 ha and further than 100 m from any other polygon in either Layer A or B that is greater than ...
- 9
1
vote
1
answer
46
views
Specifying the raster layer name in processing qgis:rastercalculator
I have a QgsRasterLayer and want to process it in a processing script with qgis:rastercalculator. How can I customize the name under which the layer is referenced in the expression? It seems that QGIS ...
- 9,877
1
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0
answers
42
views
QGIS 'Packing Problem'?
I have 45 irregular polygons (geographic areas) of various sizes. I need to grid each one into a universal number of same-sized squares/rectangles (same sized within each polygon, not necessarily ...
2
votes
1
answer
51
views
How do I convert a PyQGIS script to a processing tool with user input?
My code selects points in a layer by date and creates a new layer from them. I want to make this a processing tool where the user can choose the date and run the script.
I'm brand new to QGIS, but I'...
- 95
1
vote
1
answer
44
views
Running qgis_process from Linux terminal
I am currently working with coordinate data that I cannot take off of a remote server and I need to run QGIS processes on this data. However, in downloading QGIS 3.18.3 onto the remote machine through ...
- 11
1
vote
1
answer
41
views
processing.createAlgorithmDialog not filling default enum parameter
not sure if this is the expected behavior of the QgsProcessingParameterEnum. I have a very very example Processing script. Not doing anything in the processAlgorithm method because I'm focused on the ...
- 3,114
0
votes
0
answers
40
views
Error in Clipping Polygon
I tried Clipping my polygon after union but it gave me this error:
QGIS version: 3.26.0-Buenos Aires
QGIS code revision: 0aece2818e
Qt version: 5.15.3
Python version: 3.9.5
GDAL version: 3.5.0
GEOS ...
- 95
1
vote
2
answers
66
views
Adding ToolButton Merge Selected Features to plugin
I've created my own plugin which also includes Standard QGIS-ToolButtons.
I've been trying to add the "Merge Selected Features" (Advanced Digitize Tool Bar) Tool into my Plugin.
How do I ...
- 61
0
votes
0
answers
70
views
QGIS 3.22 does not display Google Earth after added as a XYZ tile
I am new to QGIS, I need to add Google Earth as an XYZ tile, I did this by clicking it, then hitting new connection then using the Google Earth link, and hitting okay. I then tried to view it but it ...
0
votes
0
answers
18
views
Excluding fields from alg.FIELD
Is it possible to exclude some fields from showing in processing algorithm's interface ?
@alg.input(type=alg.SOURCE, name="INPUT", label="my_layer")
@alg.input(
type=alg....
- 564
2
votes
1
answer
65
views
Get access to QgsProcessingAlgorithmDialogBase methods and attributes from within QgsProcessingAlgorithm
I was wondering if there is a simple method to have access to methods and attributes of the QgsProcessingAlgorithmDialogBase class from within a Processing script.
I can do it from outside, creating ...
- 3,114
3
votes
2
answers
130
views
Making dissolve output as temporary layer using PyQGIS
I want to dissolve my layer by using this script and it is successful, however I want my dissolved layer to be temporary, and my input as any active layer. Can someone help me?
from qgis import ...
- 95
2
votes
1
answer
49
views
QgsProcessingParameterEnum check all option by default
I'm building a Processing script with some QgsProcessingParameterEnum parameters that accept multiple values.
I cannot find an option to have by default all the options checked when opening the dialog ...
- 3,114
4
votes
1
answer
89
views
Change the symbology of a vector output layer that is returned from a processing tool?
I want to change the symbology of a Vector Output Layer that is Returned after running a Processing Tool. I am building a processing plugin. I am trying to make the effects reflect in the displayed ...
- 43
3
votes
1
answer
231
views
QGIS 3.16, 3.22. SAGA tools not working. ERROR: Loading resulting layers The following layers were not correctly generated
I've tried multiple SAGA processing tools (Tools tried include: "clip raster with polygon". "Fill sinks Fill sinks (Wang and Liu)". "Polygon Centroids.". It seems that ...
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vote
0
answers
19
views
QGIS Modeller- PostgreSQL execute and load- prevent layers being added to map?
I have a model which loads a bunch of PostGIS layers, does some processing, then adds the styled output to the map.
A side effect of the 'PostgreSQL execute and load' algorithm is that it loads those ...
- 340
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vote
1
answer
56
views
QGIS: Preserving the band values in Hillshade
I used Raster -> Analysis -> Hillshade without changing any default values and I realised that the elevation data has changed from actual metres to 1 to 255:
Is it possible to preserve the ...
- 209
0
votes
0
answers
22
views
Getting wrong coordinate system with $y function [duplicate]
I have a shapefile that I need to add Lat Lon attributes to attribute table. I am using the $y but the number I get is not from the correct coordinate system I want. I have changed the coordinate ...
- 191
3
votes
2
answers
102
views
Include the processing tool "exporttospreadsheet" into my plugin
I made a Plugin containing features for a specific workflow.
As the last function I wanted to add the qgis processing tool "ExportToSpreadsheet" (Layertool) into my plugin. It's a native ...
- 61
0
votes
1
answer
35
views
Convert smoothened contour in QGIS ( vector) to raster for use in HECRAS
I have generated contours in QGIS using point data (AutoCAD file) and I had to also smoothen the contours and remove noises (smaller contours) from the contour generated. I need to get this contour ...
- 105
8
votes
1
answer
393
views
Avoiding too curly contours in QGIS
I had point data in DXF and generated contours using QGIS. The contours had smaller islands and the contours in itself are too curly. I smoothed the contours too and I could avoid that unwanted island ...
- 105
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0
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89
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Support Vector Machine (SVM) using QGIS
I want to classify Sentinel-2 images using QGIS and SVM. Please provide me with guidelines/instructions or a video tutorial link. I'm new to QGIS. I observed that there are numerous videos for SVM ...
- 13
1
vote
1
answer
170
views
QGIS crashes when using "Split with lines" tool
I want to use the "Split with line" tool on a dataset with 5000 line features. It works if I select some of the lines, but on the whole dataset, it crashes.
Is there a way to solve/work ...
- 267
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votes
0
answers
21
views
QGIS: Group together polygon overlaps
I have a point layer with 400 locations. See the following fictituous sample. Here is the process of getting the below table:
Import CSV to get points and assocated ID
Create radii per row using ...
1
vote
1
answer
68
views
How to add a column in one shapefile that is the sum of values in another shapefile?
I am trying to calculate a weighted average CN value for 500 drainage area catchments (S1-S500).
I have one file named "DA" which has S1-S500.
Name Total_Area
S1 1.5
S2 0.8
........
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0
votes
0
answers
16
views
Setting a default value for reference layer - QgsProcessingParameterMultipleLayers
I want to have a default selected layer when running a processing algorithm.
(QgsProcessingParameterMultipleLayers).
At the moment I can achieve that by adding the defaultValue argument in ...
- 233
1
vote
0
answers
35
views
QGIS model builder: Export model to pyqgis and add some more processing steps
I have set up a processing model with the QGIS model builder. I want this model now as python script to hardcode some of the inputs (so the client does not have to select dozens of input layers each ...
- 2,486
2
votes
1
answer
47
views
Layer not visible under Raster Calculator but visible in the Tree Panel
I have one raster layer(generated inside a plugin) visible under the Tree layers panel and on the canvas but not in the Raster Calculator processing tool.
I can replicate the same behavior with the ...
- 233
1
vote
1
answer
47
views
Displaying water movement paths over grid in QGIS
I have an external .csv file with "From" cell, "To" cell, X, Y coordinates for the "From" cell, X Y coordinates for "To" cell and flow rate for water going from ...
- 11
0
votes
0
answers
62
views
Creating unique ID for overlapping polygons in QGIS
In QGIS I created a union from a layer that had a lot of overlapping polygons. In the union layer, I used the Field Calculator (see the formula I used below) to count how many overlaps there were, as ...
0
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0
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33
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Matching lower level shapefiles with higher level shapefiles
I was trying to combine two shapefiles with different levels of administrative units. when I run it, it is showing error like this.
Feature (344) from “Sector_Boundary_2006” has invalid geometry. ...
