The numerical value of the diameter of the window.
Details
It is intended that this function compute the
diameter of a window of arbitrary shape,
i.e. the maximum distance between any two points
in the window.
The current implementation just computes
the length of the diagonal of the rectangular frame
surrounding the window.
The argument w should be a window (an object of class
"owin", see owin.object for details)
or can be given in any format acceptable to as.owin().