I'm mapping areas in QGIS 2.12 based on average pricing, using area polygons (PostGIS) joined with a CSV data table that doesn't have values for areas that didn't have any sales.

I'd like to color the areas that don't have matching "area" values in my data table, but also use a green to red ramp on the areas that do have pricing.

My data is set up like this:

  • area, avgprice, sales
  • A, 50000, 100
  • B, 100000, 50
  • D, 250000, 20
  • etc.

I was able to set up a zero value with white as the coloring, and 5 other colors encompassing the total average price range, but I can't seem to Classify NULL as a value to use in the color ramp. enter image description here

Maybe there is a way to use a categorized style, but I don't if there is a way to set value ranges instead of distinct values for that methodology.


2 Answers 2


You could duplicate the layer in the Layers panel and give the duplicate a rule based style displaying only the null values, setting the rule as, for example, "area" is null.


One way is to set Null values as NaN or some unused no like -9999.0 and make another class for this.

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