R: Documentation

help {base} | R Documentation

## Documentation

### Description

These functions provide access to documentation. Documentation on a topic with name `name` (typically, an R object or a data set) can be printed with either `help(name)` or `?name`.

### Usage

    help(topic, offline = FALSE, package = .packages(),
         lib.loc = NULL, verbose = getOption("verbose"),
         try.all.packages = getOption("help.try.all.packages"),
         htmlhelp = getOption("htmlhelp"),
         pager = getOption("pager"))
    ?topic
    type?topic

### Arguments

`topic` | a name or character string on which documentation is sought (but not a variable containing a character string!).
`offline` | a logical indicating whether documentation should be displayed on-line to the screen (the default) or hardcopy of it should be produced.
`package` | a name or character vector giving the packages to look into for documentation. By default, all packages in the search path are used.
`lib.loc` | a character vector of directory names of R libraries, or `NULL`. The default value of `NULL` corresponds to all libraries currently known. If the default is used, the loaded packages are searched before the libraries.
`verbose` | logical; if `TRUE`, the file name is reported.
`try.all.packages` | logical; see `Notes`.
`htmlhelp` | logical (or `NULL`). If `TRUE` (which is the default after `help.start` has been called), the HTML version of the help will be shown in the browser specified by `options("browser")`. See `help.start` for details of the browsers that are supported.
`pager` | the pager to be used for `file.show`.
`type` | the special type of documentation to use for this topic; for example, if the type is `class`, documentation is provided for the class with name `topic`. The function `topicName` returns the actual name used in this case.

### Details

In the case of unary and binary operators and control-flow special forms, the name may need to be quoted.

If `offline` is `TRUE`, hardcopy of the documentation is produced by running the LaTeX version of the help page through `latex` (note that LaTeX 2e is needed) and `dvips`. Depending on your `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 `latexcmd` and `dvipscmd`, or the environment variables `R_LATEXCMD` and `R_DVIPSCMD` appropriately. The appearance of the output can be customized through a file ``Rhelp.cfg`' somewhere in your LaTeX search path.

### 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 printed (but no help is shown). N.B. searching all packages can be slow.

The help files can be many small files. On some file systems it is desirable to save space, and the text files in the ``help`' directory of an installed package can be zipped up as a zip archive ``Rhelp.zip`'. Ensure that file ``AnIndex`' remains un-zipped. Similarly, all the files in the ``latex`' directory can be zipped to ``Rhelp.zip`'.

### See Also

`help.search()` for finding help pages on a ``vague'' topic. `help.start()` which opens the HTML version of the R help pages; `library()` for listing available packages and the user-level objects they contain; `data()` for listing available data sets; `methods()`.

See `prompt()` to get a prototype for writing `help` pages of private packages.

### Examples

    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 package is not loaded

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

    topi <- "women"
    help(topi) ##--> Error: No documentation for `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'

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