find.package: Find Packages

Description

Find the paths to one or more packages.

Usage

find.package(package, lib.loc = NULL, quiet = FALSE,
             verbose = getOption("verbose"))
path.package(package, quiet = FALSE)

Arguments

package

character vector: the names of packages.

lib.loc

a character vector describing the location of R library trees to search through, or NULL. The default value of NULL corresponds to checking the loaded namespace, then all libraries currently known in .libPaths().

quiet

logical. Should this not give warnings or an error if the package is not found?

verbose

a logical. If TRUE, additional diagnostics are printed, notably when a package is found more than once.

Value

A character vector of paths of package directories.

Details

find.package returns path to the locations where the given packages are found. If lib.loc is NULL, then loaded namespaces are searched before the libraries. If a package is found more than once, the first match is used. Unless quiet = TRUE a warning will be given about the named packages which are not found, and an error if none are. If verbose is true, warnings about packages found more than once are given. For a package to be returned it must contain a either a Meta subdirectory or a DESCRIPTION file containing a valid version field, but it need not be installed (it could be a source package if lib.loc was set suitably).

find.package is not usually the right tool to find out if a package is available for use: the only way to do that is to use require to try to load it. It need not be installed for the correct platform, it might have a version requirement not met by the running version of R, there might be dependencies which are not available, ….

path.package returns the paths from which the named packages were loaded, or if none were named, for all currently attached packages. Unless quiet = TRUE it will warn if some of the packages named are not attached, and given an error if none are.

Examples

Run this code

# NOT RUN {
try(find.package("knitr"))
## will not give an error, maybe a warning about *all* locations it is found:
find.package("kitty", quiet=TRUE, verbose=TRUE)

## Find all .libPaths() entries a package is found:
findPkgAll <- function(pkg)
  unlist(lapply(.libPaths(), function(lib)
           find.package(pkg, lib, quiet=TRUE, verbose=FALSE)))

findPkgAll("MASS")
findPkgAll("knitr")
# }