code: function(inPositions) {
  			// the least recent touch and the most recent touch determine the bounding box of the gesture event
  			var p = inPositions;
  			// center the first touch as 0,0
  			return {
  				magnitude: p.h,
  				xcenter: Math.abs(Math.round(p.fx + (p.x / 2))),
  				ycenter: Math.abs(Math.round(p.fy + (p.y / 2)))
  			};
  		}
docs: find bounding box