QLNet.GeneralStatistics.variance C# (CSharp) Метод

        public double variance()
        {
            if (variance_ == null) {
                int N = samples();
                if (!(N > 1)) throw new ApplicationException("sample number <=1, unsufficient");
                // Subtract the mean and square. Repeat on the whole range.
                // Hopefully, the whole thing will be inlined in a single loop.
                double s2 = expectationValue(x => Math.Pow(x.Key * x.Value - mean(), 2), x => true).Key;

                //compose(square<Real>(), std::bind2nd(std::minus<Real>(), mean())), () => true).Key;
                variance_ = s2 * N / (N - 1.0);
            }
            return variance_.GetValueOrDefault();
        }