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Jun 23, 2011

How to make a geographic map chart in JMP

Here are three animated GIFs showing how to make three variations of geographic maps in JMP.

The most common type of map is the choropleth or thematic map where each region is colored by some measure variable. Making the map only takes two steps in Graph Builder:

  1. Drag in the region name variable.
  2. Drag in the coloring variable.

The rest of the animation shows some geographic panning and zooming, which is a little different than usual since there is a geographic projection applied.




A well-known problem with choropleths is that the geographic region sizes give unbalanced visual weight to each region. For the world countries, some are even too small to see. The next animation shows an alternative called a geospatial scatterplot where each region is represented by a marker at its centroid.

For that, start with the the same two steps as above and then switch the element type to Points. Adding another variable into the size role will make the sizes of the markers proportional to the values. The final step in the animation (partly off-view) uses the Marker Size property to scale all the markers to fit the map better.




Another alternative to the misleading region sizes is to artifically size the regions by some meaningful variable to create a cartogram. In JMP, the regions are sized in place without shape distortion, which makes this a noncontiguous cartogram. JMP does have some special hinting for the US that allows it to give more space to some small eastern states that have high populations, as seen in this animation where states are sized by electoral votes.




 Notice that for US states, JMP automatically adds insets for Alaska and Hawaii.

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