R in a Nutshell, 2nd Edition

Chapter 4. R Packages

A package is a related set of functions, help files, and data files that have been bundled together. Packages in R are similar to modules in Perl, libraries in C/C++, and classes in Java.

Typically, all the functions in the package are related: for example, the stats package contains functions for doing statistical analysis. To use a package, you need to load it into R (see Loading Packages for directions on loading packages).

R offers an enormous number of packages: packages that display graphics, packages for performing statistical tests, and packages for trying the latest machine learning techniques. There are also packages designed for a wide variety of industries and applications: packages for analyzing microarray data, packages for modeling credit risks, and packages for social sciences.

Some of these packages are included with R: you just have to tell R that you want to use them. Other packages are available from public package repositories. You can even make your own packages. This chapter explains how to use packages.