Geographic Information Systems Asked by Dan R on June 5, 2021
In QGIS, I have been learning a few expressions to style my trail maps but still know little and am stumped on what to use to filter my symbol data.
I am showing Parking locations on my map. I use a marker symbol as a background element, so I can do callouts. I created a data field and added values to display beside this symbol a number that references a list of parking addresses in the book’s text.
All good except if the field has no number to display, it is NULL, it does not display my marker symbol. I need to filter this, so it does show even when there is no value in the field.
So ... you are using a rule-based symbology.
I think you could try the following (even if we don't see the rules you use) :
Instead of "PLot" only try to label your sites with coalesce("PLot",'') that should enable you to handle NULL cases.
A second possibility could be to elaborate the rules of your symbology a bit more in order to exclude these NULL cases. (that means test your values using IF conditions)
Answered by Snaileater on June 5, 2021
Modify the data in PLot to contain a space instead of a Null. Then the problem may go away. Or use a ? to indicate to the viewer that the number of the lot is unknown. That may be important. Features without attributes are usually not as good as features with attributes.
Answered by wingnut on June 5, 2021
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