code: public void addSeries( String seriesName, double[] x, double[] y ) {
          XYSeries series = new XYSeries(seriesName);
          for( int i = 0; i < x.length; i++ ) {
              series.add(x[i], y[i]);
          }
          dataset.addSeries(series);
      }
docs: Add a new series by name and data.
  
  @param seriesName the name.
  @param x the x data array.
  @param y the y data array.