Introduction and Preliminaries

S-PLUS is an integrated suite of software facilities for data manipulation, calculation and graphical display. Among other things it has

• an effective data handling and storage facility,
• a suite of operators for calculations on arrays, in particular matrices,
• a large, coherent, integrated collection of intermediate tools for data analysis,
• graphical facilities for data analysis and display either at a workstation or on hardcopy, and
• a well developed, simple and effective programming language which includes conditionals, loops, user defined recursive functions and input and output facilities. (Indeed most of the system supplied functions are themselves written in the S-PLUS language.)

The term ``environment'' is intended to characterize it as a fully planned and coherent system, rather than an incremental accretion of very specific and inflexible tools, as is frequently the case with other data analysis software.

S-PLUS is very much a vehicle for newly developing methods of interactive data analysis. As such it is very dynamic, and new releases have not always been fully upwardly compatible with previous releases. Some users welcome the changes because of the bonus of new technology and new methods that come with new releases; others seem to be more worried by the fact that old code no longer works. Although S-PLUS is intended as a programming language, in my view one should regard programmes written in S-PLUS as essentially ephemeral.

The name S (or S-PLUS), as with many names within the UNIX world, is not explained, but left as a cryptic puzzle, and probably a weak pun. However its authors insist it does not stand for ``Statistics''!

These notes will be mainly concerned with S-PLUS, an enhanced version of S distributed by Statistical Sciences, Inc., Seattle, Washington.

• Reference manuals
• S-PLUS and X-windows
• Using S-PLUS interactively
• An introductory session
• S-PLUS and UNIX
• Getting help with functions and features
• S-PLUS commands. Case sensitivity.
• Recall and correction of previous commands
  • S-PLUS
  • Vanilla S
• Executing commands from, or diverting output to, a file
• Data directories. Permanency. Removing objects.