Lexical scope and statistical computing

Programming environments such as S and Lisp-Stat have languages for perform ing computations, data storage mechanisms, and a graphical interface. These languages provide an interactive interface to data analysis that is invalu able. To take full advantage of these programming environments, statisticia ns must understand the differences between them. Ihaka and Gentleman introd uced R, a version of S which uses a different scoping regimen. In some ways this makes R behave more like Lisp-Stat. This article discusses the concep t of scoping rules and shows how lexical scope can enhance the functionalit y of a language.