Accord.Math.HilbertTransform.FHT C# (CSharp) Method

        public static void FHT(Complex[] data, FourierTransform.Direction direction)
        {
            int N = data.Length;

            // Forward operation
            if (direction == FourierTransform.Direction.Forward)
            {
                // Makes a copy of the data so we don't lose the
                //  original information to build our final signal
                Complex[] shift = (Complex[])data.Clone();

                // Perform FFT
                FourierTransform.FFT(shift, FourierTransform.Direction.Backward);

                //double positive frequencies
                for (int i = 1; i < (N / 2); i++)
                {
                    shift[i] *= 2.0;
                }
                // zero out negative frequencies
                //  (leaving out the dc component)
                for (int i = (N / 2) + 1; i < N; i++)
                {
                    shift[i] = Complex.Zero;
                }

                // Reverse the FFT
                FourierTransform.FFT(shift, FourierTransform.Direction.Forward);

                // Put the Hilbert transform in the Imaginary part
                //  of the input signal, creating a Analytic Signal
                for (int i = 0; i < N; i++)
                    data[i] = new Complex(data[i].Real, shift[i].Imaginary);
            }

            else // Backward operation
            {
                // Just discard the imaginary part
                for (int i = 0; i < data.Length; i++)
                    data[i] = new Complex(data[i].Real, 0.0);
            }
        }