I have a chart (in this case a geographic map) that I want to filter down to show only some countries based on a selection in a control. I do not simply want to set all countries to 0, as this will keep them highlighted.

I would like some way to automatically create a copy of my original data variable that is filtered to contain the data only in the categories that correspond to the selection, setting the other categories to NA or missing. That way, my map will show only the countries selected in any colored highlight, and all other countries will be white or not look as if they have data.