US Maps in R

A really great read (it's a chapter) about the use of maps in R (at least, US maps specifically), from Kieran Healy's Data Visualization. What are you trying to show with your map? What is your data? Is it spatial? Or, maybe it's actually about population, so why is Montana bigger than Connecticut?

There are some great projections, there's the standard geographical one, and the weird "geography squished into population size" one (Figure 7.1, lower left), and the electoral college/population one isn't bad depending on what you are trying to do (Figure 7.1, lower right), although I end up liking the one that makes all the states the same size, each a square (statebins, in section 7.3). (Of course, what is a state? They are not all comparable at all! What is Washington, D.C.? Why not Puerto Rico? Etc.!)

No post about maps is complete without XKCD's heatmap comic and another on map projections, as well as a link to the segment from The West Wing about map projections which everyone should watch.