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The R-Commander GUI consists of a window containing several menus, buttons, and information fields. (The menu tree, etc., are shown below.) In addition, the Commander window contains script and output text windows. The R-Commander menus are easily configurable through a text file or, preferably, through plug-in packages.

The menus lead to simple dialog boxes, the general contents of which are more or less obvious from the names of the menu items. These boxes have a common structure, including a help button leading to the help page for a relevant function.

By default, commands generated via the dialogs are posted to the output window, along with printed output, and to the script window. Lines in the script window can be edited and (re)submitted for execution. Error messages, warnings, and "notes" appear in a messages window.

Commands access a current or active data set (data frame). When a new data set is read (from an attached package or imported), it becomes the active data set. The user can also select an active data set from among data frames currently in memory.

In addition to standard packages, the Commander uses functions in a number of other packages: abind, aplpack, car, colorspace, effects, Hmisc, leaps, lmtest, multcomp, relimp, rgl, and (on Windows) RODBC. To install the Rcmdr package along with all of these and their dependencies, use the command install.packages("Rcmdr", dependencies=TRUE). If any of these packages are missing, the Rcmdr will offer to install them when it starts up. Note: These other packages also have dependencies, which have dependencies, etc., so many packages get installed; with a fast Internet connection, the process should go reasonably quickly, however.

My object in designing and implementing this GUI was to cover the content of a basic-statistics course. The target text was Moore's The Basic Practice of Statistics, Second Edition (Freeman, 2000), which is the text that I used for a two-semester introduction to statistics for undergraduate sociology majors. The R Commander implements the content of this text plus some additional material (e.g., linear and generalized linear models). As a result of several suggestions that I have received, the coverage is now larger than originally envisaged.

I must confess that I'm not terribly enamored of menu/dialog box interfaces to statistical software, but I do feel that these interfaces have a role for introductory and occasional use. The Commander interface is not innovative, but I hope that it's simple and familiar. One of my design goals was to wean users from the GUI to writing commands, which is one motivation for the script window.

The procedure for installing the R Commander under Mac OS X is more complicated, so please read and follow these instructions carefully. These instructions and the associated files are intended for Mac OS X 10.5 (Leopard) or 10.6 (Snow Leopard) systems. I assume that you've already installed R.

* Check to see if the X11 windowing system (X Windows) has already been installed on your computer (as is probably the case): The file X11.app should appear in the Utilities folder under Applications in the finder. If X11.app is missing, you can install it from your Mac OS X installation disc as follows:

o Insert your Mac OS X install disc. (If you have two discs it will be on the"Install Disc 1").
o Double click on Optional Installs.
o Double click on Optional Installs.mpkg, then click Continue and accept the license agreement.
o Click the triangle next to Applications in order to expand the list of applications.
o Check "X11", and then click Continue and Install. Click Close when the installation finishes.