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AN INTRODUCTION TO R

The package functionality is available after attaching the package by R> library("sandwich") A comprehensive list of available packages can be obtained from

http://CRAN.R-project.org/src/contrib/PACKAGES.html

Note that on Windows operating systems, precompiled versions of packages are downloaded and installed. In contrast, packages are compiled locally before they are installed on Unix systems.

1.3 Help and Documentation

Roughly, three different forms of documentation for the R system for statis- tical computing may be distinguished: online help that comes with the base distribution or packages, electronic manuals and publications work in the form of books etc.

The help system is a collection of manual pages describing each user-visible function and data set that comes with R. A manual page is shown in a pager or web browser when the name of the function we would like to get help for is supplied to the help function

R> help("mean") or, for short, R> ?mean

Each manual page consists of a general description, the argument list of the documented function with a description of each single argument, information about the return value of the function and, optionally, references, cross-links and, in most cases, executable examples. The function help.search is helpful for searching within manual pages. An overview on documented topics in an add-on package is given, for example for the sandwich package, by

R> help(package = "sandwich")

Often a package comes along with an additional document describing the pack- age functionality and giving examples. Such a document is called a vignette (Leisch, 2003, Gentleman, 2005). The sandwich package vignette is opened using

R> vignette("sandwich", package = "sandwich")

More extensive documentation is available electronically from the collection of manuals at

http://CRAN.R-project.org/manuals.html

For the beginner, at least the first and the second document of the following four manuals (R Development Core Team, 2005a,b,c,d) are mandatory:

An Introduction to R: A more formal introduction to data analysis with R than this chapter.

R Data Import/Export: A very useful description of how to read and write various external data formats.

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