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DataPRO/FftSharp/Experimental.cs

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+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace FftSharp
+{
+    [Obsolete("This module is for educational purposes only")]
+    public static class Experimental
+    {
+        // An easy-to-read (but non-optimized) implementation of the FFT algorithm
+        private static Complex[] FFTsimple(Complex[] input)
+        {
+            Complex[] output = new Complex[input.Length];
+
+            int H = input.Length / 2;
+            Complex[] evens = new Complex[H];
+            Complex[] odds = new Complex[H];
+            for (int i = 0; i < H; i++)
+            {
+                evens[i] = input[2 * i];
+                odds[i] = input[2 * i + 1];
+            }
+            odds = FFTsimple(odds);
+            evens = FFTsimple(evens);
+
+            double mult1 = -2 * Math.PI / input.Length;
+            for (int i = 0; i < H; i++)
+            {
+                double radians = mult1 * i;
+                odds[i] *= new Complex(Math.Cos(radians), Math.Sin(radians));
+            }
+
+            for (int i = 0; i < H; i++)
+            {
+                output[i] = evens[i] + odds[i];
+                output[i + H] = evens[i] - odds[i];
+            }
+
+            return output;
+        }
+
+        // Compute the forward or inverse discrete Fourier Transform (not using the fast FFT algorithm)
+        public static Complex[] DFT(Complex[] input, bool inverse = false)
+        {
+            int N = input.Length;
+            double mult1 = (inverse) ? 2 * Math.PI / N : -2 * Math.PI / N;
+            double mult2 = (inverse) ? 1.0 / N : 1.0;
+            Console.WriteLine($"REAL {mult1} {mult2}");
+
+            Complex[] output = new Complex[N];
+            for (int k = 0; k < N; k++)
+            {
+                output[k] = new Complex(0, 0);
+                for (int n = 0; n < N; n++)
+                {
+                    double radians = n * k * mult1;
+                    Complex temp = new Complex(Math.Cos(radians), Math.Sin(radians));
+                    temp *= input[n];
+                    output[k] += temp * mult2;
+                }
+            }
+
+            return output;
+        }
+
+        public static Complex[] DFT(double[] input, bool inverse = false)
+        {
+            return DFT(Transform.MakeComplex(input), inverse);
+        }
+    }
+}