r project for statistical computing
The r project for statistical computing is an open source companion
to S, S-Plus, successor to XLispStat, and
more.
Whereas SAS and SPSS will give copious output from a regression
or discriminant analysis, R will give minimal output and store the
results in a fit object for subsequent interrogation by further R
functions.
manuals [HTML]
Sample R session
R 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 directly at the computer or on hardcopy.
* a well developed, simple and effective programming
language (called `S') 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 language.)