subtract

A method to subtract one SWPoint from another SWPoint.

Parameter	Value
point1: a point set object (SWPoint)	isn93 map point locations.
point2: a point set object (SWPoint)	isn93 map point locations.

Return	Value
object:	A point set object (SWPoint).

Example:

var point1 = SWPoint.create(359583, 406481);

var point2 = SWPoint.create(359603, 406471);

var point = SWPoint.subtract(point1, point2);