Even if you think you don’t know what a choropleth map is, chances are you’ve seen one. And come November 2012, you’ll see plenty: one iconic example of a choropleth map is a map of the United States, laid out in red and blue, showing the results of a presidential election.
Choropleth maps can be simple, like in the example above, where the color of the state indicates whether the state goes in one direction (Democrat) or the other (Republican). The states can also be colored on a scale to indicate data, with a color like blue representing a low number and red representing a high number, leaving a number in between to be purple.
These simple visualizations make large amounts of data easy to understand at a glance, allowing insights that would take much longer if you’re looking at a table of numbers. But the process of making these maps is not easily apparent.
There have been tutorials for... keep reading