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I'm working and creating a large amount of maps using the latest version of Qgis with vector files and corresponding data sheets. Usually, there will be missing values which is usually easily avoided by assigning these data values to "NULL" and adding an additional layer below the graduated one with a constant color, however when there are "several missing" values i run out of ideas of how to easily handle these.

If say i have two missing values, one with "NULL" and one with "-999", the "-999" values will mess with Qgis' automatic interval determination tools since it regards the -999 value as relevant - Is there any way to tell Qgis to ignore this value?

It seems as though the Feature Subset feature it is greyed out in my vector file - even though the vector file is in edit mode. This seems to be connected with the fact that my vector file is joined with an external data file - Is it really not possible to filter joined data?


From other questions here at stackexchange i learned that the query builder sadly doesn't work with joined layers - the only solution was to join layers, save as a new layer and apply the subset features here.

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Go to the Layer Properties | General tab and set a subset query which filters out all missing values, e.g.

my_value IS NOT NULL AND my_value != -999

In QGIS 2.10, it will be possible to filter joined layers. In previous versions that's not possible.

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