.packages returns information about package availability.
a character vector describing the location of R
library trees to search through, or
.packages() returns the names of the currently
attached packages invisibly whereas
.packages(all.available = TRUE) gives (visibly) all
packages available in the library location path
For a package to be regarded as being ‘available’ it must have valid
metadata (and hence be an installed package). However, this will
report a package as available if the metadata does not match the
directory name: use
find.package to confirm that the
metadata match or
installed.packages for a much slower
but more comprehensive check of ‘available’ packages.
A character vector of package base names, invisible unless
all.available = TRUE.
.packages(all.available = TRUE) is not a way to find out if a
small number of packages are available for use: not only is it
expensive when thousands of packages are installed, it is an
incomplete test. See the help for
find.package for why
require should be used.
Guido Masarotto for the
all.available = TRUE part of
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