perspEmpty: perspEmpty
Creates a persp plot without drawing anything in the interior.
Does equivalent of plot( type="n") for persp.
Description
Regression demonstrations require a blank slate in which
points and planes can be drawn. This function creates
that blank persp canvas for those projects. It is not
necessary that x1, x2 and y be vectors of the same
length, since this function's only purpose is to plot an
empty box with ranges determined by the input variables.
persp calls the 3 axes x, y, and z, but here they are
called x1, x2, and y.