"R is both a strongly functional programming language and a
general environment for statistical exploration of data sets. As an
environment, R allows you to create many graphical representations
of data from a custom command line...
"As with the interactive shells of Python, Ruby, wish for
Tcl/Tk, or many Lisp environments, the R shell is a great way to
explore operations--command recall and editing let you try
variations on commands. In contrast to many other programming
language interactive shells, but in keeping with the data-centric
nature of R, the R shell will optionally save a complete
environment (one per working directory)..."