help
Documentation
help is the primary interface to the help systems.
- Keywords
- documentation
Usage
help(topic, package = NULL, lib.loc = NULL,
verbose = getOption("verbose"),
try.all.packages = getOption("help.try.all.packages"),
help_type = getOption("help_type"))Arguments
- topic
- usually, a name or character string specifying the
topic for which help is sought. A character string (enclosed in
explicit single or double quotes) is always taken as naming a topic.
If the value of
topicis a length-one character vector the topic is taken to be the value of the only element. Otherwisetopicmust be a name or a reserved word (if syntactically valid) or character string.See
Details for what happens if this is omitted. - package
- a name or character vector giving the packages to look
into for documentation, or
NULL. By default, all packages whose namespaces are loaded are used. To avoid a name being deparsed use e.g.(pkg_ref)(see the examples). - lib.loc
- a character vector of directory names of Rlibraries,
or
NULL. The default value ofNULLcorresponds to all libraries currently known. If the default is used, the loaded packages are searched before the libraries. This is not used for HTML help (seeDetails . - verbose
- logical; if
TRUE, the file name is reported. - try.all.packages
- logical; see
Note. - help_type
- character string: the type of help required.
Possible values are
"text","html"and"pdf". Case is ignored, and partial matching is allowed.
Details
The following types of help are available:
- Plain text help
- HTML help pages with hyperlinks to other topics, shown in a
browser by
browseURL. #ifdef unix (Where possible an existing browser window is re-used: the OS X GUI uses its own browser window.) #endif If for some reason HTML help is unavailable (seestartDynamicHelp), plain text help will be used instead. - For
helponly, typeset as PDF -- see the section onOffline help .
The rendering of text help will use directional quotes in suitable
locales (UTF-8 and single-byte Windows locales): sometimes the fonts
used do not support these quotes so this can be turned off by setting
options(useFancyQuotes = FALSE).
topic is not optional: if it is omitted Rwill give
- If a package is specified, (text or, in interactive use only, HTML) information on the package, including hints/links to suitable help topics.
- If
lib.loconly is specified, a (text) list of available packages. - Help on
helpitself if none of the first three arguments is specified.
Some topics need to be quoted (by backticks) or given as a
character string. These include those which cannot syntactically
appear on their own such as unary and binary operators,
function and control-flow reserved words (including
if, else for, in, repeat,
while, break and next). The other reserved
words can be used as if they were names, for example TRUE,
NA and Inf.
If multiple help files matching topic are found, in interactive
use a menu is presented for the user to choose one: in batch use the
first on the search path is used. (For HTML help the menu will be an
HTML page, otherwise a graphical menu if possible if
getOption("menu.graphics") is true, the default.)
Note that HTML help does not make use of lib.loc: it will
always look first in the loaded packages and then along
.libPaths().
Note
Unless lib.loc is specified explicitly, the loaded packages are
searched before those in the specified libraries. This ensures that
if a library is loaded from a library not in the known library trees,
then the help from the loaded library is used. If lib.loc is
specified explicitly, the loaded packages are not searched.
If this search fails and argument try.all.packages is
TRUE and neither packages nor lib.loc is
specified, then all the packages in the known library trees are
searched for help on topic and a list of (any) packages where
help may be found is displayed (with hyperlinks for help_type =
"html"). NB: searching all packages can be slow, especially
the first time (caching of files by the OS can expedite subsequent
searches dramatically).
Offline help
Typeset documentation is produced by running the LaTeX version of the
help page through The appearance of the output can be customized through a file
If there is a function Rd.sty. Some
environment variables are consulted, notably getOption("papersize")) and offline_help_helper in the workspace or
further down the search path it is used to do the typesetting,
otherwise the function of that name in the utils namespace (to
which the first paragraph applies). It should accept at least two
arguments, the name of the LaTeX file to be typeset and the type
(which is nowadays ignored). It accepts a third argument,
texinputs, which will give the graphics path when the help
document contains figures, and will otherwise not be supplied.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
See Also
? for shortcuts to help topics.
help.search() or ?? for finding help pages
on a vague topic;
help.start() which opens the HTML version of the Rhelp pages;
library() for listing available packages and the
help objects they contain;
data() for listing available data sets;
methods().
Use prompt() to get a prototype for writing help
pages of your own package.
Examples
library(utils)
help()
help(help) # the same
help(lapply)
help("for") # or ?"for", but quotes/backticks are needed
try({# requires working TeX installation:
help(dgamma, help_type = "pdf")
## -> nicely formatted pdf -- including math formula -- for help(dgamma):
system2(getOption("pdfviewer"), "dgamma.pdf", wait = FALSE)
})
help(package = "splines") # get help even when package is not loaded
topi <- "women"
help(topi)
try(help("bs", try.all.packages = FALSE)) # reports not found (an error)
help("bs", try.all.packages = TRUE) # reports can be found
# in package 'splines'
## For programmatic use:
topic <- "family"; pkg_ref <- "stats"
help((topic), (pkg_ref))