/** Initializes the animation. */
 public void initialize() {
   double x = control.getDouble("initial x");
   double y = control.getDouble("initial y");
   double z = control.getDouble("initial z");
   double dt = control.getDouble("dt");
   lorenz.initialize(x, y, z);
   lorenz.ode_solver.initialize(dt);
   frame.setVisible(true);
 }