\Header{data}{Data Sets}
\alias{print.packageIQR}{data}
\keyword{documentation}{data}
\keyword{datasets}{data}
\begin{Description}\relax
Loads specified data sets, or list the available data sets.\end{Description}
\begin{Usage}
\begin{verbatim}
data(..., list = character(0), package = .packages(),
     lib.loc = NULL, verbose = getOption("verbose"))
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{...}] a sequence of names or character strings.
\item[\code{list}] a character vector.
\item[\code{package}] a name or character vector giving the packages to look
into for data sets.  By default, all packages in the search path are
used, then the \file{data} directory (if present) of the current
working directory.
\item[\code{lib.loc}] a character vector of directory names of \R{} libraries,
or \code{NULL}.  The default value of \code{NULL} corresponds to all
libraries currently known.  If the default is used, the loaded
packages are searched before the libraries.
\item[\code{verbose}] a logical.  If \code{TRUE}, additional diagnostics are
printed.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
Currently, four formats of data files are supported:

\Enumerate{
\item files ending \file{.RData} or \file{.rda} are
\code{\Link{load}()}ed.

\item files ending \file{.R} or \file{.r} are
\code{\Link{source}()}d in, with the \R{} working directory changed
temporarily to the directory containing the respective file.

\item files ending \file{.tab} or \file{.txt} are read using
\code{\Link{read.table}(..., header = TRUE)}, and hence result in
a data frame.

\item files ending \file{.csv} are read using
\code{\Link{read.table}(..., header = TRUE, sep = ";")},
and also result in a data frame.
}

The data sets to be loaded can be specified as a sequence of names or
character strings, or as the character vector \code{list}, or as both.

If no data sets are specified, \code{data} lists the available data
sets.  It looks for a file \file{00Index} in a \file{data} directory
of each specified package, and uses these files to prepare a listing.
If there is a \file{data} area but no index a warning is given: such
packages are incomplete.  The information about available data sets is
returned in an object of class \code{"packageIQR"}.  The structure of
this class is experimental.  In earlier versions of R, an empty
character vector was returned along with listing available data sets.

If \code{lib.loc} is not specified,  the datasets are searched for
amongst those packages already loaded, followed by the \file{data}
directory (if any) of the current working directory and then packages
in the specified libraries.  If \code{lib.loc} \emph{is} specified,
packages are searched for in the specified libraries, even if they are
already loaded from another library.

To just look in the \file{data} directory of the current working
directory, set \code{package = NULL}.\end{Details}
\begin{Value}
a character vector of all data sets specified, or information about
all available data sets in an object of class \code{"packageIQR"} if
none were specified.\end{Value}
\begin{Note}\relax
The data files can be many small files.  On some file systems it is
desirable to save space, and the files in the \file{data} directory of
an installed package can be zipped up as a zip archive
\file{Rdata.zip}.  You will need to provide a single-column file
\file{filelist} of file names in that directory.

One can take advantage of the search order and the fact that a
\file{.R} file will change directory.  If raw data are stored in
\file{mydata.txt} then one can set up \file{mydata.R} to read
\file{mydata.txt} and pre-process it, e.g. using \code{transform}.
For instance one can convert numeric vectors to factors with the
appropriate labels.  Thus, the \file{.R} file can effectively contain
a metadata specification for the plaintext formats.\end{Note}
\begin{SeeAlso}\relax
\code{\Link{help}} for obtaining documentation on data sets,
\code{\Link{save}} for \emph{creating} the first (\file{.rda}) kind of
data, typically the most efficient one.\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
data()                      # list all available data sets
data(package = base)        # list the data sets in the base package
data(USArrests, "VADeaths") # load the data sets `USArrests' and `VADeaths'
help(USArrests)             # give information on data set `USArrests'
\end{ExampleCode}
\end{Examples}

