* label around the right point
*/
CircleDrawer cd = new CircleDrawer(
Color.red, new BasicStroke(1.0f), null
);
XYAnnotation locationSelected = new XYDrawableAnnotation( xx, yy, 11, 11, cd );
plot.addAnnotation(locationSelected);
XYPointerAnnotation pointer = new XYPointerAnnotation(
formatAnnotation( xx, yy).toString(), xx, yy, Math.PI - knob.getAngle() );
pointer.setBaseRadius(35.0);
pointer.setTipRadius(10.0);