R

"R is a language and environment for statistical computing and graphics". R facilitates a wide variety of statistical and graphical techniques for data manipulation, calculation, and graphical display. R is characterized as an environment as opposed to being a tool because it is a "fully planned and coherent system, rather than an incremental accretion of very specific and inflexible tools". "One of R's strengths is the ease with which well-designed publication-quality plots can be produced, including mathematical symbols and formulae where needed. Great care has been taken over the defaults for the minor design choices in graphics, but the user retains full control". R is an open source program and is freely available.