This book explains the basics of S-PLUS in a clear style at a level suitable for people with little computing or statistical knowledge. Unlike the manuals, it is not comprehensive, but instead introduces the most important ideas of S-PLUS and R, its companion in implementing the S language. The authors take the reader on a journey into the world of interactive computing, data exploration, and statistical analysis. They explain how to approach data sets and teach the corresponding S-PLUS commands. A collection of exercises summarizes the main ideas of each chapter. The exercises are accompanied by solutions that are worked out in full detail, and the code is ready to use and to be modified. The volume is rounded off with practical hints on how efficient work can be performed in S-PLUS, for example by pointing out how to set up a good working environment and how to integrate S-PLUS with office products. The book is well suited for self-study and as a textbook. It serves as an introduction to S-PLUS as well as R. A separate chapter points out the major differences between R and S-PLUS. Over the last editions, the book has been updated to cover important changes like the inclusion of S Language Version 4, Trellis graphics, a graphical user interface, and many useful tips and tricks. The fourth edition is based on S-PLUS Version 7.0 for Windows and UNIX and has been updated and revised accordingly.