/**
  * Get y-value from epsilon
  *
  * @param epsilon epsilon
  * @return y-Value
  */
 protected double getYFromEpsilon(double epsilon) {
   OPTICSPlot opticsplot = optics.getOPTICSPlot(context);
   int h = opticsplot.getHeight();
   double y = opticsplot.getScale().getScaled(epsilon, h - .5, .5) / (double) h * plotheight;
   return (y < 0.) ? 0. : (y > plotheight) ? plotheight : y;
 }
 /**
  * Get epsilon from y-value
  *
  * @param y y-Value
  * @return epsilon
  */
 protected double getEpsilonFromY(double y) {
   OPTICSPlot opticsplot = optics.getOPTICSPlot(context);
   y = (y < 0) ? 0 : (y > plotheight) ? 1. : y / plotheight;
   return optics.getOPTICSPlot(context).scaleFromPixel(y * opticsplot.getHeight());
 }