R is a language and an environment for statistical computing. It is similar to the S language developed at AT&T Bell Laboratories by Rick Becker, John Chambers and Allan Wilks. There are versions of R for the Unix, Windows Architectures and operating systems on which R runs and Mac families of operating systems. Moreover, R runs on different computer architectures like Intel, PowerPC, Alpha systems and Sparc systems. R was initially developed by Ihaka and Gentleman (1996) both from the University of Auckland, New Zealand. The current development of R is carried out by a core team of a dozen people from different institutions around the world. R development takes advantage of a growing community that cooperates in its development due to its open source philosophy. In effect, the source code of every R component is freely available for inspection and/or adaptation. There are many critics to the open source model. Most of them mention the lack of support as the main drawback of open source software. It is certainly not the case with R! There are many excellent documents, books and sites that provide free information on R. Moreover, the excellent R-help mailing list is a source of invaluable advice and information, much better then any amount of money could ever buy! There are also searchable mailing lists archives1 that you can use before posting a question.