Mapping the Iowa caucus results: how it’s done with R

January 6, 2012

(This article was first published on Revolutions, and kindly contributed to R-bloggers)

If you've been following the presidential primary process here in the US, you've probably seen many maps of the results of the Iowa caucuses by now (such as this infamous one from Fox News). But you might be interested to learn how such maps can be made using the R language.

The Offensive Politics blog explains the process in detail, from accessing the data (helpfully provided as a Google Fusion table), to using R packages (including maptools, ggplot2, RColorBrewer, and gpclib) to transform and chart the table, and creating heat maps like this one, showing the percentage point advantage Romney had over Santorum in each Iowa county:

You can find more such charts, along with the detailed instructions and R code, at the link below.