void AddData()
        {
            dc.DataSeriesList.Clear ();
            // Add Sine data:
            ds = new DataSeries();
            for (int i = 0; i < 21; i++)
                ds.AddPoint (new CGPoint (.5f * i, 2f + (float)Math.Sin (.5f * i)));
            dc.Add (ds);

            // Add Cosine data:
            ds = new DataSeries ();
            for (int i = 0; i < 21; i++) {
                ds.AddPoint (new CGPoint (.5f * i, 2f + (float)Math.Cos (.5f * i)));
            }
            dc.Add (ds);

            // Add another Sine data:
            ds = new DataSeries();
            for (int i = 0; i < 21; i++) {
                ds.AddPoint(new CGPoint (.5f * i, 3f + (float)Math.Sin (.5f * i)));
            }
            dc.Add (ds);

            cm = new ColorMap (dc.DataSeriesList.Count, 150);
            dc.CMap = cm.Summer ();
        }