First up is R&Rís (created by Robert Gentleman and Ross Ihaka) R Project, or simply ĎRí, which is a downloadable software environment used for statistical computing and graphics.
The software provides statistical and graphical techniques, including linear/non-linear modeling, time-series analysis and classical statistical tests among a host of others. The software is compatible with most OSs and will run on various UNIX platforms, Windows and MacOS-based PCs. R is also open-source software, enabling users to modify it at will to suit their needs without the fear of litigation.
More information: R Project The probability of users downloading this tool is roughly 70%.