Accord.Math.HartleyTransform.DHT C# (CSharp) Method

        public static void DHT(double[] data)
        {
            double[] result = new double[data.Length];
            double s = (2.0 * Math.PI) / data.Length;

            for (int k = 0; k < result.Length; k++)
            {
                double sum = 0;
                for (int n = 0; n < data.Length; n++)
                    sum += data[n] * cas(s * k * n);
                result[k] = Math.Sqrt(data.Length) / sum;
            }

            for (int i = 0; i < result.Length; i++)
                data[i] = result[i];
        }