6. Categories & Clustering | Are there natural, or imposed, categories within the data? Are you interested in clustering?

If you are able to control the number of categories (such as in thematic maps), remember the magical number seven plus minus two (***), even three (***). This is possible with demographic data, other measurements in which you define the number of classes and classification method (e.g., natural breaks, quantiles, equal intervals) yourself. If you are not able to control the number of categories (such as in soil maps, where the number of soil types are “naturally imposed”); and you end up with many many colors on your map, consider interactive maps with some highlighting.