Choropleth Maps

Unlike the previously discussed maps, which did not use predefined regions (states, countries etc), choropleth maps use the shapes of the regions.

These maps are very popular and they are easy to use and interpret. However, they can be easily misused, resulting in misinterpretation and deceit.

• We must be very careful in choosing the level of detail for the regions (i.e. countries/states/counties/regions...)

• We must also use color maps carefully

• Choropleth maps, when used to depict categorical information, cannot be used to depict quantities (they can only use one channel at a time)

  

  For example, in the map above, we can only visualize red/blue i.e. which party received majority votes in a region, but cannot visualize the number of votes per region. This gives a very partial view of the data.