Accessing exported and internal variables, i.e.R objects (including lazy loaded data sets) in a namespace.
package name: symbol or literal character string.
variable name: symbol or literal character string.
For a package pkg,
pkg::name returns the value of the
name in namespace
pkg:::name returns the value of the internal variable
name. The package namespace will be loaded if it was not
loaded before the call, but the package will not be attached to the
Specifying a variable or package that does not exist is an error.
pkg::name does not access the objects in the
package:pkg (which does not exist until the
package's namespace is attached): the latter may contain objects not
exported from the namespace. It can access datasets made available by