Showing multiple variables on a map is an age old challenge in data visualization and cartography. Here we review this design space. This investigation began as a personal curiosity, and expanded to a quest to find the solution to what appears to be an unsolved problem in data visualization — how to calculate the color that one perceives when looking at a particular region of a dot density map. Dot density maps, small multiples, multivariate choropleths, oh my!

Dot density maps (sometimes called dot distribution maps) show little dots that are randomly distributed within polygons on a map. One dot…

Curran Kelleher

Data Visualization Consultant

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