CanvasCommon.DensityClusteringModel.GetDistance C# (CSharp) Метод

        private double? GetDistance(int segmentsLength, int tmpIndex, int runOrderIndex)
        {
            if (tmpIndex < runOrderIndex)
            {
                // the dissimilarity between (column) i and j is retrieved from index [n*i - i*(i+1)/2 + j-i-1].
                return this.Distance[segmentsLength * tmpIndex - (tmpIndex * (tmpIndex + 1)) / 2 + runOrderIndex - tmpIndex - 1];
            }
            else if (tmpIndex > runOrderIndex)
            {
                return this.Distance[segmentsLength * runOrderIndex - (runOrderIndex * (runOrderIndex + 1)) / 2 + tmpIndex - runOrderIndex - 1];
            }
            else
            {
                return null;
            }
        }