pointqgissymbology
How to display different symbols (not different in size, different in shape and color) on the same point in QGIS 2.8 using Point Displacement renderer?
I want my layout with symbols around the centroid of areas, and symbols from rule-based renderer.
For some reason it seems QGIS forces all the symbols to be the same.
Worse case scenario I will do it manually.
I've only used the Graduated Symbol renderer; however, the categorized symbol marker seems to be quite similar. I was also seeking what you were and here was my solution:
# replace
QgsSymbolV2.defaultSymbol(layer.geometryType())
# with
sym = QgsMarkerSymbolV2.createSimple({'name' : 'triangle', 'color' : 'red'})
'triangle' in place of whatever marker you would like displayed and 'red' in place of whatever color you would like.
That just fixed my problem.
You can sort of do this by setting the width in the "Symbol" dialogue - at least I think this can be used to do what you want.
Set the classification to color and classify your data. Then click on change symbol and select the line type (default Simple Line). From this dialogue you can set a pen width based on an attribute. It won't by default allow you to define an expression but if you use the 'width assistant' and then go back into the menu it will let you use the edit and this brings up the standard expression generator.
Best Answer
If you render your points as you want to see them AFTER you've applied the Point Displacement renderer, you still have full access to the original renderer style through the point displacement dialogue:
In the above image you can click the 'renderer settings' button, and it opens a mini-version of the renderer dialogue box that allows you to alter the colour, size, transparency of the points as if you were styling them without the point displacement.
You can see that in my example, I have first rendered the points using a Categorized renderer, then applied point displacement, then gone back into the 'Renderer Settings' and applied a size scale to the points...