This is a very helpful article. I had been looking at expensive commercial packages. This article, and my following through the tutorial, convinced me to give R a try.
One issue is that scatterplot does not appear to be a supported function in the current R release. However, the plot function appears have to taken on all the capabilities of the scatterplot function that the article used. It would be nice if the article could get updated to reflect that. Otherwise, I hope people notice this note when they get confused.