void GetNDC(TCanvas & c, double xin, double yin, double & x, double & y) {
c.Update();//this is necessary!
//printf("x %g, x1 %g, x2 %g, xr %g\n", xin, c.GetX1(), c.GetX2(), c.GetX2()-c.GetX1());
//printf("y %g, y1 %g, y2 %g, yr %g\n", yin, c.GetY1(), c.GetY2(), c.GetY2()-c.GetY1());
x = (c.XtoPad(xin) - c.GetX1())/(c.GetX2()-c.GetX1());
y = (c.YtoPad(yin) - c.GetY1())/(c.GetY2()-c.GetY1());
}
