volume(x) The function volume is generic, with methods for
the classes "box3" (three-dimensional boxes) and
"boxx" (multi-dimensional boxes).
There is also a method for the class "owin"
(two-dimensional windows), which is identical to
area.owin,
and a method for the class "linnet" of linear networks,
which returns the length of the network.
area.owin,
volume.box3,
volume.boxx,
volume.linnet