R is an Open Source project that is an implementation of the S programming language that was developed to provide an environment for Statistical Analysis. The creators consider the system to be an environment where statistical methods and graphical display can be accessed in a flexible and powerful way.
One way in which the system is powerful is the readily availability of a large number of additional packages that can be downloaded and installed from the R Project website – in fact the Windows version of R has a simple interface for this task.
Another strength of R is the facilities that are available for creating high quality graphical displays, including an implementation of the Trellis graphics concepts – called lattice. The Trellis graphics paradigm is an attempt to allow graphical investigation of data with more than two variables (dimensions) and is based on dividing the data into subsets based on one or more variables and producing a plot (of common type) for each of these subsets. Another advantage of using Trellis is the definition of a consistent look to the graphics.
For many users the system may not appear to be easy to use due to the lack of a typical graphical user interface, but the absence of a point and click interface to access the many methods that are available should not be a barrier to discourage the initial effort required to become proficient in using R.
Other useful resources are provided on the Supplementary Material page.