help.search {base} | R Documentation |
Allows for searching the help system for documentation matching a given character string in the (file) name, alias, title, or keyword entries (or any combination thereof), using either fuzzy matching or regular expression matching. Names and titles of the matched help entries are nicely displayed.
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, 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" , "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 to be matched in the help page topics and title. |
keyword |
a character string to be matched in the help page keywords. |
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 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. |
agrep |
if NULL (the default) and the character string to
be matched consists of alphanumeric characters, whitespace or a dash
only, approximate (fuzzy) matching via agrep is used;
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, 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.
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.
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") 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.