Maps are tricky, especially quantitative choropleth maps. Not because they are hard to make in Tableau. Just the opposite, it takes just a few mouse clicks to make one but is it right? It depends on the data. When you drop a continuous measure on the Filled Map, Tableau creates a choropleth map and assigns a unique shade of color to each mark – a sequential color palette.

When your data is normally distributed, this default setup might be just what you need…

… but it often isn’t and the color assignment requires further exploration.

Overview of map classing

Cartographers use several different methods of aggregating features into classes, all with a single purpose of making spotting patterns in the data easier. The maps above are examples of Unclassified Scheme where every mark (polygon) with a unique data value receives a unique shade of grey…

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