private void addScatterSeries(DataSeries item, PerformanceIndex index) {
   Volatility volatility = index.getVolatility();
   ILineSeries series =
       chart.addScatterSeries(
           new double[] {volatility.getStandardDeviation()},
           new double[] {index.getFinalAccumulatedPercentage()},
           item.getLabel());
   item.configure(series);
 }