R is an open source system widely used in statistics, bioinformatics and finance field etc. It's
data structure and working environment are perfect for analysis of large sized data.
Many classical and modern statistical algorithms are implemented.
A lot of packages in various fields make it really powerful. The R Project home page is http://www.r-project.org.
R packages address is (http://CRAN.R-project.org).
RStudio is a popular IDE (integrated development environment) for R.
Many books about R are freely available at http://cran.r-project.org/doc/contrib/.
» R Installation and Quick Start