Bayesian Decision Boundaries

I started reading The Elements of Statistical Learning by Hastie, Tibshirani, and Friedman, and was curious about how to reproduce Figure 2.5. (The book is made available as a free and legal pdf here.) So I figured out how to produce similar figures using Mathematica. I assume that this is also fairly straightforward to do in R, but I don’t yet know enough R. The authors explain the sampling method on pages 16 and 17.