private void ComputeRelativePerf(int i)
        {
            KeyValuePair <DateTime, double> p = datesAndValuation.ElementAt(i);
            DateTime currentDate = p.Key;
            int      benchIdx = index.findDateIndex(currentDate);
            double   perfC = perf.ElementAt(i), perfB = index.GetPerformanceAt(benchIdx);

            relativePerf.Add((double)(perfC - perfB));
        }