I´ve got some polygons that I want to colourize by multiple columns. Can this be done or will I have to edit the attributes? Some polygons only have data-attributes in 1 one column, where as other have data in both column 1,2 and 3. I´m thinking of the concept like the pie chart function in the diagrams-function in layer properties. In this case I want my polygons splitted in colors by the values in the columns.
If I understand you correctly, your polygons will be colored based on multiple data columns. There are two ways to do this:
- Create a new data column and use the field calculator to classify your polygons based your data
- Use rule based styling (preferably!). This is a complex topic, but this excellent blog post will get you started, and there is additional online material available, e.g. by linfiniti or even QGIS' documentation (use search).
You can define rule-based symbology, which then allows you to create the rules using the usual QGIS expression builder.
In this example, I created just 2 rules, one with one field, the other with two fields. You open the expression builder with .... in the Rule properties window.