I am working on a map of mortality rates for several racial/ethnic groups and I have created custom classes to encompass the rates instead of the QGIS classes created through its various modes. This is to create a standard set of groupings and to minimize confusion created by different ranges being given similar coloring schemes across groups.
The problem I am having lies in the fact that some groups are not represented in all the classes. For instance, a range from 0 to 1200 with classes of 300 (0-300, 300-600, and so on). One group never goes above 600 while another group never falls below that level. And the print composer, at least as far as I've been able to identify, will not include those classes which are empty.
To allow for a visual comparison between the maps, however, I would like the legend symbols to be present even if they are not used in the map. The reader can parse from the colors on the map that some of the categories are not fulfilled and it allows for easier interpretation for a reader comparing the maps side-to-side.
I'm hoping this is a simple issue where I've just missed something.