Choropleth Legend Format

Earlier I posted about Choropleth Limitations. Choropleth maps have legends that show how the colors (or shades of gray, perhaps) match with the values they represent. There are a few different options for the presentation of these legends. In ArcMap, the legend defaults to a vertical style with the highest value (largest number) on the bottom of the list and the lowest value is at the top of the list like this:

I often prefer to push the colors together for a continuous color scheme like this by changing the ArcMap setting to 0 for “patches (vertically).” I also sometimes prefer to change the numbers to Courier New or some other monospaced typeface since numbers line up nicely when they are placed vertically. Like this:

However, I’m currently reading through a book by Daniel B. Carr and Linda Williams Pickle called “Visualizing Data Patterns with Micromaps” that asserts that the high value should be on top since that is how we are used to reading the y axis on graphs. This would change the legend to look like this:

I like to change it up occassionally and create a horizontal legend. I would think that Carr and Pickle would be okay with this since it reads from left to right the same way you would read the x axis on a graph, from low to high:

  1. #1 by @thorlakur on May 9, 2012 - 9:34 am

    Interesting post on choropleth legend format

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