[GIS] QGIS coloring NULL values

categorized-renderercolornullqgis

I am using QGIS Version 2.14.3.
I have a map with polygons and a lot of different attributes. Some polygons have NULL values in some columns.
I've tried to color the polygons with properties->style->graduated. But in some columns half of the values are NULL and now they don't have any colour.

I know that i could color the NULL values when I chose "categorized" coloring, but I have way to many different entries to do that, because QGIS chooses a colour for every different entry.

I need to have intervals for coloring. Is there an easy way to do that?

Best Answer

Sounds like you need to use rule based styling.

Basically, you will create a few rules. One will be "field_name" IS NULL, and the others will be "field_name" <= 20 AND "field_name" >= 11.

Related Solutions

[GIS] Using expression string builder to ignore NULL values in QGIS

Found a link which contained solutions to adding 2 layers or more:

https://stackoverflow.com/questions/1769648/addition-with-null-values

Basic gist is when using 2 columns:

coalesce("Column_1"+"Column_2","Column_1","Column_2")

Using 3 columns or more, I used:

coalesce("Column_1",0.00) + coalesce("Column_2",0.00) + coalesce("Column_3",0.00) + .......

QGIS Symbology – How to Symbolize Features with NULL Values

As @MichaelMiles-Stimson already mentioned, there doesn't seem to be a way to symbolise NULL features. However, there is an alternative whereby you create a filter to force QGIS to treat NULL values as an integer such as 0. I've included an example where I created 3 simple polygons each with a certain value:

3 polygons

Attribute table

Here is the Graduated Symbology I used with the following command:

case when "Some_Value" IS NULL then 0 else "Some_Value" end

Graduated symbology

Hope this helps!

Best Answer

Related Solutions

[GIS] Using expression string builder to ignore NULL values in QGIS

QGIS Symbology – How to Symbolize Features with NULL Values

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