Choropleth Counties

By Ross Perez 04 Avr, 2011

Choosing how to display data is often the most difficult part of the data visualization process. Would a bar chart be superior to a pie? Perhaps a scatter would tell more than two bar charts? One of the most difficult of these choices is between filled maps (choropleth) and shapes.

Choropleth maps have several advantages. First, they avoid overlap and because of it they are usually very neat and beautiful. Choropleth maps also tend to make it easy to spot trends geographically, like the clusters of major cities in the household income map above.

However, shapes also have some interesting traits. First of all, it can be much easier to spot small outliers. You may notice how Los Alamos County, NM stands out in the bottom view, but is nearly invisible in the top view. Shapes also have the relative advantage of not distorting by size, because they give equal weight to each mark. This can be frustrating though, since they can overlap, as in the eastern US with this map.

Regardless of your choice, it is relatively easy to create both types of map in Tableau. For the choropleth map, you will need a polygon file, but once you have that it is a simple data blend away. If you have an interest, you can download the US counties polygon file used to make this map, courtesy of Alan Smithee.


Submitted by James Baldwin (non vérifié) on

This is a wonderful post. The choropleth is one of the only reasons I have kept MapPoint on my machine. This is a good work around, although I would encourage Tableau designers to incorporate that map type into a future release.

Submitted by Steve W. on

Terrific post, and the polygon file is a great contribution to the community. Alan and Ross the two of you (along with Andy Cotgreave and Joe Mako) continue to kick ass!

Submitted by Guest (non vérifié) on

I had no idea there were such basic differences or what went into representation in maps. Will obviously read up on this, thank you.

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Submitted by Jeff (non vérifié) on

I downloaded the file and am attempting to use the map with other data but with no success. How can I join the files I'm working with to the this polygon file to get the results shown above? My data is in an access table which includes State abbreviation, County name, and County FIPS codes.


Submitted by manas (non vérifié) on

Choose the display mode data is often the hardest part of the process of data visualization. Can a bar chart is more than a cake? Perhaps it could spread over two bar graphs? One of the most difficult choices between meeting cards (choropleth) and shapes.
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