optional additional arguments to be passed to or from methods.
Details
Although users would normally call data.frame,
the as.data.frame function is the underlying workhorse that
enables a mondate to be stored in a data.frame.
When array-shaped mondates are stored,
the number of rows is retained and if the dimension > 2 it is
"flattened" in the
usual data.frame sense.
The mondate method is fashioned after
the as.data.frame.Date method.