R is a language and environment for statistical computing and graphics. It is a GNU project that provides a wide variety of statistical (linear and nonlinear modelling, classical statistical tests, time-series analysis, classification, clustering, etc.) and graphical techniques, and is highly extensible. While a software like SAS can be more amendable to large datasets, R is versatile, well documented and free to use.

For more information, visit www.r-project.org.