public double getDirectionAngleChange(){
		double sum = 0;
		long preX = mousePointer.getXpix(), preY = mousePointer.getYpix();
		double preAngle=0,a,da;
		boolean isFirst = true;
		if (0 == mouseMoves.size()) return 0;
		int index = noSkipFirstPoint()?0:1;
		MouseMove mouseMove;
		for (;index<mouseMoves.size();index++) {
			mouseMove = mouseMoves.get(index);
			a = get2PointDirectionAngle(preX, preY, mouseMove.getXpix(), mouseMove.getYpix());
			if (isFirst){
				isFirst = false;
			}else{
				da = preAngle - a;
				if (da<-180)
					sum += da+360;
				else
					sum += da-360;
			}
			preAngle = a;
			preX = mouseMove.getXpix();
			preY = mouseMove.getYpix();
		}
		if (noSkipLastPoint()){
			a = get2PointDirectionAngle(preX, preY, mousePointer.getXfinalpix(), mousePointer.getYfinalpix());
			da = preAngle - a;
			if (da<-180)
				sum += da+360;
			else
				sum += da-360;
		}
		return sum/mouseMoves.size();
	}