library and require load and attach add-on packages.
library(package, help, pos = 2, lib.loc = NULL,
character.only = FALSE, logical.return = FALSE,
warn.conflicts, quietly = FALSE,
verbose = getOption("verbose"),
mask.ok, exclude, include.only,
attach.required = missing(include.only))require(package, lib.loc = NULL, quietly = FALSE,
warn.conflicts,
character.only = FALSE,
mask.ok, exclude, include.only,
attach.required = missing(include.only))
conflictRules(pkg, mask.ok = NULL, exclude = NULL)
the name of a package, given as a name or
literal character string, or a character string, depending on
whether character.only is FALSE (default) or
TRUE.
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().
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 to
.libPaths().
Non-existent library trees are silently ignored.
a logical indicating whether package or
help can be assumed to be character strings.
logical. If it is TRUE, FALSE or
TRUE is returned to indicate success.
logical. If TRUE, warnings are
printed about conflicts from attaching the new
package. A conflict is a function masking a function,
or a non-function masking a non-function. The default is TRUE
unless specified as FALSE in the conflicts.policy option.
a logical. If TRUE, additional diagnostics are
printed.
a logical. If TRUE, no message confirming
package attaching is printed, and most often, no errors/warnings are
printed if package attaching fails.
character string naming a package.
character vector of names of objects that can mask objects on the search path without signaling an error when strict conflict checking is enabled
character vector of names of objects to
exclude or include in the attached frame. Only one of these arguments
may be used in a call to library or require.
logical specifying whether required packages
listed in the Depends clause of the DESCRIPTION file
should be attached automatically.
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.
Handling of conflicts depends on the setting of the
conflicts.policy option. If this option is not set, then
conflicts result in warning messages if the argument
warn.conflicts is TRUE. If the option is set to the
character string "strict", then all unresolved conflicts signal
errors. Conflicts can be resolved using the mask.ok,
exclude, and include.only arguments to library and
require. Defaults for mask.ok and exclude can be
specified using conflictRules.
If the conflicts.policy option is set to the string
"depends.ok" then conflicts resulting from attaching declared
dependencies will not produce errors, but other conflicts will.
This is likely to be the best setting for most users wanting some
additional protection against unexpected conflicts.
The policy can be tuned further by specifying the
conflicts.policy option as a named list with the following
fields:
error:logical; if TRUE treat unresolved
conflicts as errors.
warn:logical; unless FALSE issue a warning
message when conflicts are found.
generics.ok:logical; if TRUE ignore conflicts
created by defining S4 generics for functions on the search path.
depends.ok:logical; if TRUE do not treat
conflicts with required packages as errors.
can.mask:character vector of names of packages that are allowed to be masked. These would typically be base packages attached by default.
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 recorded as accepted.
As from R 3.4.0 the license check is done when the namespace is loaded.
Free or Open Source Software (FOSS,
e.g.https://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).
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.
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.) Use .packages(all = TRUE) to
obtain just the names of all available packages, and
installed.packages() for 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.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
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.
# NOT RUN {
library() # list all available packages
library(lib.loc = .Library) # list all packages in the default library
# }
# NOT RUN {
library(help = splines) # documentation on package 'splines'
# }
# NOT RUN {
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")
# }
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