library
Loading/Attaching and Listing of Packages
library
and require
load and attach add-on packages.
- Keywords
- data
Usage
library(package, help, pos = 2, lib.loc = NULL, character.only = FALSE, logical.return = FALSE, warn.conflicts = TRUE, quietly = FALSE, verbose = getOption("verbose"))
require(package, lib.loc = NULL, quietly = FALSE, warn.conflicts = TRUE, character.only = FALSE)
Arguments
- package, help
- the name of a package, given as a name or
literal character string, or a character string, depending on
whether
character.only
isFALSE
(default) orTRUE
). - pos
- the position on the search list at which to attach the
loaded namespace. Can also be the name of a position on the current
search list as given by
search()
. - lib.loc
- a character vector describing the location of R
library trees to search through, or
NULL
. The default value ofNULL
corresponds to all libraries currently known to.libPaths()
. Non-existent library trees are silently ignored. - character.only
- a logical indicating whether
package
orhelp
can be assumed to be character strings. - logical.return
- logical. If it is
TRUE
,FALSE
orTRUE
is returned to indicate success. - warn.conflicts
- logical. If
TRUE
, warnings are printed aboutconflicts
from attaching the new package. A conflict is a function masking a function, or a non-function masking a non-function. - verbose
- a logical. If
TRUE
, additional diagnostics are printed. - quietly
- a logical. If
TRUE
, no message confirming package attaching is printed, and most often, no errors/warnings are printed if package attaching fails.
Details
library(package)
and require(package)
both load the
namespace of the package with name package
and attach it on the
search list. require
is designed for use inside other
functions; it returns FALSE
and gives a warning (rather than an
error as library()
does by default) if the package does not
exist. Both functions check and update the list of currently attached
packages and do not reload a namespace which is already loaded. (If
you want to reload such a package, call detach(unload =
TRUE)
or unloadNamespace
first.) If you want to load a
package without attaching it on the search list, see
requireNamespace
.
To suppress messages during the loading of packages use
suppressPackageStartupMessages
: this will suppress all
messages from R itself but not necessarily all those from package
authors.
If library
is called with no package
or help
argument, it lists all available packages in the libraries specified
by lib.loc
, and returns the corresponding information in an
object of class "libraryIQR"
. The structure of this class may
change in future versions. In earlier versions of R, only the names
of all available packages were returned; use .packages(all =
TRUE)
for obtaining these. Note that
installed.packages()
returns even more information.
library(help = somename)
computes basic information about the
package somename
, and returns this in an object of class
"packageInfo"
. The structure of this class may change in
future versions. When used with the default value (NULL
) for
lib.loc
, the attached packages are searched before the libraries.
Value
-
Normally
library
returns (invisibly) the list of attached
packages, but TRUE
or FALSE
if logical.return
is
TRUE
. When called as library()
it returns an object of
class "libraryIQR"
, and for library(help=)
, one of
class "packageInfo"
.require
returns (invisibly) a logical indicating whether the required
package is available.
Note
library
and require
can only load/attach an
installed package, and this is detected by having a
DESCRIPTION file containing a Built: field.
Under Unix-alikes, the code checks that the package was installed
under a similar operating system as given by R.version$platform
(the canonical name of the platform under which R was compiled),
provided it contains compiled code. Packages which do not contain
compiled code can be shared between Unix-alikes, but not to other OSes
because of potential problems with line endings and OS-specific help
files. If sub-architectures are used, the OS similarity is not
checked since the OS used to build may differ (e.g.
i386-pc-linux-gnu
code can be built on an
x86_64-unknown-linux-gnu
OS).
The package name given to library
and require
must match
the name given in the package's DESCRIPTION file exactly, even
on case-insensitive file systems such as are common on Windows and
OS X.
Licenses
Some packages have restrictive licenses, and there is a mechanism to
allow users to be aware of such licenses. If
getOption("checkPackageLicense") == TRUE
, then at first
use of a package with a not-known-to-be-FOSS (see below) license the
user is asked to view and accept the license: a list of accepted
licenses is stored in file ~/.R/licensed. In a non-interactive
session it is an error to use such a package whose license has not
already been accepted. Free or Open Source Software (FOSS, e.g.,
http://en.wikipedia.org/wiki/FOSS) packages are determined by
the same filters used by available.packages
but applied
to just the current package, not its dependencies. There can also be a site-wide file R_HOME/etc/licensed.site of
packages (one per line).
Formal methods
library
takes some further actions when package methods
is attached (as it is by default). Packages may define formal generic
functions as well as re-defining functions in other packages (notably
base) to be generic, and this information is cached whenever
such a namespace is loaded after methods and re-defined functions
(implicit generics) are excluded from the list of conflicts.
The caching and check for conflicts require looking for a pattern of
objects; the search may be avoided by defining an object
.noGenerics
(with any value) in the namespace. Naturally, if the
package does have any such methods, this will prevent them from
being used.
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
See Also
attach
, detach
, search
,
objects
, autoload
,
requireNamespace
,
library.dynam
, data
,
install.packages
and
installed.packages
;
INSTALL
, REMOVE
.
The initial set of packages attached is set by
options(defaultPackages=)
: see also Startup
.
Examples
library(base)
library() # list all available packages
library(lib.loc = .Library) # list all packages in the default library
library(help = splines) # documentation on package 'splines'
library(splines) # attach package 'splines'
require(splines) # the same
search() # "splines", too
detach("package:splines")
# if the package name is in a character vector, use
pkg <- "splines"
library(pkg, character.only = TRUE)
detach(pos = match(paste("package", pkg, sep = ":"), search()))
require(pkg, character.only = TRUE)
detach(pos = match(paste("package", pkg, sep = ":"), search()))
require(nonexistent) # FALSE
## Not run:
# ## if you want to mask as little as possible, use
# library(mypkg, pos = "package:base")
# ## End(Not run)