ggplot2 - Cartogram + choropleth map in R

Question

I've been using ggplot2 lately to create a bunch of choropleths. I was wondering if it was possible to use ggplot2 to create a map similar to this (from WorldMapper):

It's a choropleth where the shapefile polygons are distorted to represent relative population counts. I believe this is called a cartogram. They do this with a bunch of other variables. In the spirit of the Choropleth R Challenge, does anyone know how to do this using R?

Answer 1

The cartogram package, available on CRAN, has the rubber sheet distortion-style cartogram you want.