R: Search the Help System

help.search {base} | R Documentation

## Search the Help System

### Description

Allows for searching the help system for documentation matching a given regular expression in the (file) name, alias, title, or keyword entries (or any combination thereof). Topics and titles of the matched help entries are nicely displayed.

### Usage

    help.search(pattern, fields = c("alias", "title"),
                apropos, keyword, whatis, ignore.case = TRUE,
                package = NULL, lib.loc = NULL,
                help.db = getOption("help.db"),
                verbose = getOption("verbose"),
                rebuild = FALSE)

### Arguments

`pattern` | a character string containing a regular expression to be matched in the specified fields. If this is given, the arguments `apropos`, `keyword`, and `whatis` are ignored.
`fields` | a character vector specifying the fields of the help data bases to be searched. The entries must be abbreviations of `"name"`, `"alias"`, `"title"`, and `"keyword"`, corresponding to the help page's (file) name, the topics it provides documentation for, its title, and the keywords it can be classified to.
`apropos` | a character string containing a regular expression to be matched in the help page topics and title.
`keyword` | a character string containing a regular expression to be matched in the help page keywords.
`whatis` | a character string containing a regular expression to be matched in the help page topics.
`ignore.case` | a logical. If `TRUE`, case is ignored during matching; if `FALSE`, pattern matching is case sensitive.
`package` | a character vector with the names of packages to search through, or `NULL` in which case all available packages in the specified library trees `lib.loc` are searched.
`lib.loc` | a character vector describing the location of R library trees to search through, or `NULL`. The default value of `NULL` corresponds to all libraries currently known.
`help.db` | a character string giving the file path to a previously built and saved help data base, or `NULL`.
`verbose` | logical; if `TRUE`, the search process is traced.
`rebuild` | a logical indicating whether the help data base should be rebuilt.

### Details

Upon installation of a package, the Perl script ``Rd2contents.pl`' creates a ``CONTENTS`' data base which contains the information on name, aliases, title and keywords (as well as the URL of the HTML version of the help file) in Debian Control Format. This is the data base searched by `help.search()`.

The arguments `apropos` and `whatis` play a role similar to the Unix commands with the same names.

If possible, the help data base is saved to the file ``help.db`' in the ``.R`' subdirectory of the user's home directory or the current working directory.

Note that currently, the aliases in the matching help files are not displayed.

### Value

The results are returned in an object of class `"hsearch"`, which has a print method for nicely displaying the results of the query. This mechanism is experimental, and may change in future versions of R.

### See Also

`help`; `help.start` for starting the hypertext (currently HTML) version of R's online documentation, which offers a similar search mechanism.

`apropos` uses regexps and has nice examples.

### Examples

    help.search("linear models")    # In case you forgot how to fit linear
                                    # models

    help.search("print")            # All help pages with topics or title
                                    # matching `print'
    help.search(apropos = "print")  # The same

    help.search(keyword = "hplot")  # All help pages documenting high-level
                                    # plots.

    ## Help pages with documented topics starting with `try'.
    help.search("\\btry", fields = "alias")
    ## Do not use `^' or `$' when matching aliases or keywords.

[Package Contents]