How to create conditional statement in QGIS field calculator?

How to create conditional statement in QGIS field calculator?

I just tested this : You can use the condition several times: WHEN cat = 1 THEN 205 WHEN cat = 2 THEN 215 WHEN cat = 3 THEN 225 WHEN cat = 4 THEN 235 …. Something like this perhaps: Highly active question. Earn 10 reputation (not counting the association bonus) in order to answer this question.

What are the functions in the QGIS field calculator?

QGIS FIELD CALCULATOR. This group contains operators (e.g., +, -, *). This group contains functions to handle conditional checks in expressions. This group contains math functions (e.g., square root, sin and cos).

How to create a virtual field in QGIS?

You can also create a virtual field, which will automatically return an updated value in case the values in cat change (e.g. you edit the layer). Remember that the values of virtual fields will not be saved in the dataset and are only visible inside this QGIS project. I just tested this : You can use the condition several times:

Can you create a custom function in QGIS?

With the Function Editor you are able to define your own Python custom functions in a comfortable way. The function editor will create new Python files in qgis2pythonexpressions and will auto load all functions defined when starting QGIS. Be aware that new functions are only saved in the expressions folder and not in the project file.

What happens when I use the field calculator?

When you click on the field calculator icon the dialog opens (see figure_attributes_3 ). If the layer is not in edit mode, a warning is displayed and using the field calculator will cause the layer to be put in edit mode before the calculation is made.

Where do I find the raster bands in QGIS?

The Raster bands list contains all loaded raster layers that can be used. To add a raster to the raster calculator expression field, double click its name in the Fields list. You can then use the operators to construct calculation expressions, or you can just type them into the box.

How to write conditional statements in Python parser?

Writing conditional (if/then) statements into ArcGIS Field Calculator using Python Parser? I have gotten stuck on seemingly simple ArcGIS field calculator python expression. I obtained a great answer to a another similar question a few years ago: Using Range in Python expression of ArcGIS Field Calculator? .

How to write a conditional statement in ArcGIS?

Write your def function in the codeblock and call the function in the box below. When referencing a field name in the codeblock, don’t use exclamation points, but do use them in the lower box when you call the function. Indentation must be two or four spaces. Single or double quotes are acceptable for strings.

How to use the field calculator in Python?

The GUI version of the field calculator looks like this: However, I wanted to do this programmatically using python.

Where do I find the functions in QGIS?

The available functions are listed in Expressions chapter. With the Function Editor you are able to define your own Python custom functions in a comfortable way. The function editor will create new Python files in qgis2pythonexpressions and will auto load all functions defined when starting QGIS.

Where to find field calculator in QGIS 2.8?

Visit http://docs.qgis.org/2.8 for QGIS 2.8 docs and translations. The Field Calculator button in the attribute table allows you to perform calculations on the basis of existing attribute values or defined functions, for instance, to calculate length or area of geometry features.

When to use multiple case statements in QGIS?

I’m trying to avoid having to add the point layer multiple times to my project, in order to label based on different attributes. The CASE statement can include multiple attributes in multiple conditions (or even in the same condition: WHEN attribute1 = 1 AND attribute2 = 0 THEN… is legal).

Where do I find the function list in QGIS?

The Function List contains functions as well as fields and values. View the help function in the Selected Function Help. In Expression you see the calculation expressions you create with the Function List. For the most commonly used operators, see Operators.

How do you add a value to an expression in QGIS?

To add a value to the expression you are writing, double click its name in the list. Sample values can also be accessed via right-click. Select the field name from the list, then right-click to access a context menu with options to load sample values from the selected field. Fields name should be double-quoted in the expression.

How to define an operator in QGIS function?

Operators ¶ Function Description column name “column name” Value of the field column name, take car ‘string’ a string value, take care to not be conf NULL null value a IS NULL a has no value

When to use raster calculator for conditional calculation?

When A is 3 or 11, (A@1 = 3 + A@1 = 11) part returns 1. Otherwise it returns 0. Thanks for contributing an answer to Geographic Information Systems Stack Exchange!

How to add raster to raster calculator expression field?

The results are written to a new raster layer with a GDAL-supported format. The Raster bands list contains all loaded raster layers that can be used. To add a raster to the raster calculator expression field, double click its name in the Fields list.