\Header{help}{Documentation}
\alias{?}{help}
\keyword{documentation}{help}
\begin{Description}\relax
These functions provide access to documentation.
Documentation on a topic with name \code{name} (typically, an \R{}
object or a data set) can be printed with either \code{help(name)} or
\code{?name}.\end{Description}
\begin{Usage}
\begin{verbatim}
help(topic, offline = FALSE, package = .packages()
     lib.loc = .lib.loc, verbose = getOption("verbose"),
     htmlhelp = getOption("htmlhelp"))
?topic
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{topic}] a name or character string on which documentation is
sought (but \emph{not} a variable containing a character string!).
\item[\code{offline}] a logical indicating whether documentation should be
displayed on-line to the screen (the default) or hardcopy of it
should be produced.
\item[\code{package}] a name or character vector giving the packages to look
into for documentation.  By default, all packages in the search path
are used.
\item[\code{lib.loc}] A character vector of directory names of \R{} libraries.
Defaults to all libraries currently known.
\item[\code{verbose}] logical; if \code{TRUE}, the file name is reported.
\item[\code{htmlhelp}] logical (or \code{NULL}).  If \code{TRUE} (which is the
default after \code{\Link{help.start}} has been called), the HTML
version of the help will be shown in a browser.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
In the case of unary and binary operators and control-flow special
forms, the name may need to be quoted.

If \code{offline} is \code{TRUE}, hardcopy of the documentation is
produced by running the LaTeX version of the help page through
\code{latex} (note that LaTeX 2e is needed) and \code{dvips}.
Depending on your \code{dvips} configuration, hardcopy will be sent to
the printer or saved in a file.  If the programs are in non-standard
locations and hence were not found at compile time, you can either set
the options \code{latexcmd} and \code{dvipscmd}, or the environment
variables \code{R\_LATEXCMD} and \code{R\_DVIPSCMD} appropriately.
The appearance of the output can be customized through a file
\file{Rhelp.cfg} somewhere in your LaTeX search path.\end{Details}
\begin{Note}\relax
You will only get help for \R{} objects in your
\code{\Link{search}()} path, i.e., \code{help(dist)} will only work after
\code{\Link{library}(mva)}. To look in all the packages in all the
current libraries, use
\code{help(topic, package=.packages(all=T), lib.loc=.lib.loc)}

The help files can be many small files. On some file systems it is
desirable to save space, and the text files in the \file{help} directory
of an installed package can be zipped up as a zip archive
\file{Rhelp.zip}. Ensure the files \file{AnIndex} and
\file{00Titles} remain un-zipped.  Similarly, all the files in the
\file{latex} directory can be zipped to \file{Rhelp.zip}.\end{Note}
\begin{SeeAlso}\relax
\code{\Link{help.search}()} for finding help pages on a ``vague'' topic.
\code{\Link{help.start}()} which opens the HTML version of the \R{}
Manual;
\code{\Link{library}()} for listing available packages and the
user-level objects they contain;
\code{\Link{data}()} for listing available data sets;
\code{\Link{methods}()}.

See \code{\Link{prompt}()} to get a prototype for writing \code{help}
pages of private packages.\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
help()
help(help)              # the same

help(lapply)
?lapply                 # the same

help("for")             # or ?"for", but the quotes are needed
?"+"

help(package = stepfun) # get help even when it's not present

data()                  # list all available data sets
?women                  # information about data set "women"

topi <- "women"
help(topi) ##--> Error: No documentation for `topi'
\end{ExampleCode}
\end{Examples}

