Accord.Math.Transforms.FourierTransform2.DFT C# (CSharp) Method

        public static void DFT(Complex[] data, FourierTransform.Direction direction)
        {
            int n = data.Length;
            var c = new Complex[n];

            // for each destination element
            for (int i = 0; i < c.Length; i++)
            {
                double sumRe = 0;
                double sumIm = 0;
                double phim = 2 * Math.PI * i / (double)n;

                // sum source elements
                for (int j = 0; j < n; j++)
                {
                    double re = data[j].Real;
                    double im = data[j].Imaginary;
                    double cosw = Math.Cos(phim * j);
                    double sinw = Math.Sin(phim * j);

                    if (direction == FourierTransform.Direction.Backward)
                        sinw = -sinw;

                    sumRe += (re * cosw + im * sinw);
                    sumIm += (im * cosw - re * sinw);
                }

                c[i] = new Complex(sumRe, sumIm);
            }

            if (direction == FourierTransform.Direction.Backward)
            {
                for (int i = 0; i < c.Length; i++)
                    data[i] = c[i] / n;
            }
            else
            {
                for (int i = 0; i < c.Length; i++)
                    data[i] = c[i];
            }
        }