Splus is a statistical analysis package marketed by MathSoft. It runs on many Unix based systems and on Microsoft Windows. Splus has at its core a programming language called S which originates from AT&T Bell Labs, this language includes functions for manipulating matrix and vector data; the Splus system extends the language with a large set of functions for statistical analysis and visualisation of multivariate data. Splus provides an interactive command based interface to statistical analysis although newer versions on the Windows platform incorporate many GUI controls for statistical analysis. This environment is very useful for some kinds of speech analysis since it is optimised for vector and matrix operations and provides excellent facilities for generating publication quality graphics.
In addition to the core statistical and graphics functions built into the Splus environment, the Emu/Splus extensions provide functions for importing, analysing and visualising speech data in Splus from an Emu database. These functions work identically on the Unix and Windows versions of Splus.
Splus is a commercial system and offers an excellent range of statistical and graphical functions as well as being fully supported by Mathsoft and it's international resellers. In some contexts though, Splus can be expensive, especially for teaching purposes where each student might require a personal copy. There now exists a freely available `clone' of Splus called R which is largely compatible with Splus at the source code level -- that is most functions in Splus work identically in R. R is made freely available by Robert Gentleman and Ross Ihaka of the University of Auckland in New Zealand, more information can be found via the Comprehensive R Archive Network (CRAN). R is currently a work-in-progress but may be useful to some groups; it runs on most Unix systems and Windows, a Macintosh port exists but is not up to date as of this writing. All of the Emu/Splus extensions have been tested under R and work identically to their Splus counterparts.
A similar set of extensions exist for the Xlisp-Stat system which is a Lisp-based statistics system similar in motivation to Splus. The Emu/Xlisp-Stat extensions are documented elsewhere in this manual. All of these interfaces use generic Emu facilities for importing speech data from a database -- the same techniques could be used to interface to other data visualisation and analysis systems such as Matlab, Sciplot or various spreadsheet systems. Users are encouraged to contact the authors if they are interested in writing such an interface.