R is an implementation of the S language that was originally developed by J. M. Chambers at AT&T’s Bell Laboratories. The original S is licensed to the Insightful Corporation which sells an enhanced version called S-PLUS. S-PLUS is rather expensive and really not that much better than the the freely (GNU) available R so why not use R?
Many of the examples in this introductory course are borrowed from chapters 1 and 2 of Modern Applied Statistics with S-PLUS (MASS) by W. N. Venables and B. D. Ripley. Despite the title, the current version deals with both R and S-PLUS. MASS is a good investment, you should consider buying it or at least getting it from the library before someone else does.
