R is an integrated suite of software facilities for data manipulation, calculation and graphical display. It includes an effective data handling and storage facility; a suite of operators for calculations on arrays, in particular matrices; a large, coherent, integrated collection of intermediate tools for data analysis; graphical facilities for data analysis and display either on-screen or on hardcopy, and; a well-developed, simple and effective programming language which includes conditionals, loops, user-defined recursive functions and input and output facilities.