XEmacs is a highly customizable
open source text editor and application development system. It is the
editor I use, and it is available for most modern operating systems
including Linux, Windows and OS X. It is by far the best way to use
R. A viable alternative is Tinn-R. For more general
information, see the XEmacs
homepage and the XEmacs entry on
Wikipedia. You may also be interested in Emacs (of which XEmacs is a fork).
On OS X, the easiest way to get Emacs+ESS is by using AquamacsEmacs which is a distribution
of Emacs that comes preconfigured with a large number for packages
that make Emacs feel more like an OS X program. OS X standard keyboard
shortcuts are supported, files open in separate windows, nice fonts
are available, and it has a convenient drag & drop installer. An
alternative is to use Fink
to install XEmacs. Fink is
the easy way to install and manage Unix software on OS X. It is an OS
X port of the Debian Linux system
administration tools.
If you are using Linux or another Un*x
operating system, it should be obvious to you how to install XEmacs
and ESS. You may also want to use John Fox's configure
script.