| help.search {utils} | R Documentation |
Allows for searching the help system for documentation matching a given character string in the (file) name, alias, title, concept or keyword entries (or any combination thereof), using either fuzzy matching or regular expression matching. Names and titles of the matched help entries are displayed nicely.
help.search(pattern, fields = c("alias", "concept", "title"),
apropos, keyword, whatis, ignore.case = TRUE,
package = NULL, lib.loc = NULL,
help.db = getOption("help.db"),
verbose = getOption("verbose"),
rebuild = FALSE, agrep = NULL)
pattern |
a character string 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", "title", "alias", "concept", and
"keyword", corresponding to the help page's (file) name, its
title, the topics and concepts it provides documentation for, and
the keywords it can be classified to. |
apropos |
a character string to be matched in the help page topics and title. |
keyword |
a character string to be matched in the help page
‘keywords’. ‘Keywords’ are really categories: the
standard categories are listed in file ‘RHOME/doc/KEYWORDS’
(see also the example) and some package writers have defined their
own. If keyword is specified, agrep defaults to
FALSE. |
whatis |
a character string 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 library trees specified by 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. |
agrep |
if NULL (the default unless keyword is
used) and the character string to
be matched consists of alphanumeric characters, whitespace or a dash
only, approximate (fuzzy) matching via agrep is used
unless the string has fewer than 5 characters; otherwise, it is
taken to contain a regular expression to be matched via
grep. If FALSE, approximate matching is not
used. Otherwise, one can give a numeric or a list specifying the
maximal distance for the approximate match, see argument
max.distance in the documentation for agrep. |
Upon installation of a package, a contents data base which contains
the information on name, title, aliases and keywords and, concepts
starting with R 1.8.0, is computed from the Rd files in the package and
serialized as ‘Rd.rds’ in the ‘Meta’ subdirectory of the
top-level package installation directory (or, prior to R 1.7.0, as
‘CONTENTS’ in Debian Control Format with aliases and keywords
collapsed to character strings in the top-level package installation
directory). This, or a pre-built help.search index serialized as
‘hsearch.rds’ in the ‘Meta’ directory, 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.
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.
help;
help.start for starting the hypertext (currently HTML)
version of R's online documentation, which offers a similar search
mechanism.
RSiteSearch to access an on-line search of R resources.
apropos uses regexps and has nice examples.
help.search("linear models") # In case you forgot how to fit linear
# models
help.search("non-existent topic")
## Not run:
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.
file.show(file.path(R.home(), "doc", "KEYWORDS")) # show all keywords
## Help pages with documented topics starting with 'try'.
help.search("\\btry", fields = "alias")
## Do not use '^' or '$' when matching aliases or keywords
## (unless all packages were installed using R 1.7 or newer).
## End(Not run)