h2D</h4>
<ul>
<li> In case all the points are in the same Z-plane Z0 (zmin = zmax), the graph
     minimum is set to Z0-0.01*Z0 and the maximum to Z0+0.01*Z0. This
     allow to make <tt>TGraph2D</tt> like:
     <pre>
     {
        double *x = new double[2];
        double *y = new double[2];
        double *z = new double[2];
        x[0] = 6215.;
        x[1] = 5542.;
        y[0] = 3853.;
        y[1] = 5270.;
        z[0] = 2723.;
        z[1] = 2723.;
        TGraph2D * g = new TGraph2D(2, x, y, z);
 