Discrete Fourier Transform (Go)

fourier.go

/*
* By Simon Jürgensmeyer, 2014.
* based on the work of Nayuki Minase:
* http://nayuki.eigenstate.org/page/how-to-implement-the-discrete-fourier-transform
 */

package main

import "fmt"
import "math"

func main() {
	var inSlice = []complex128{
		complex(1, 0),
		complex(2, 0),
		complex(3, 0),
		complex(4, 0),
		complex(5, 0),
		complex(9, 0),
		complex(7, 0),
		complex(5, 0),
		complex(3, 0),
		complex(1, 0),
	}

	var result []complex128 = fourier(inSlice)

	for _, element := range result {
		fmt.Printf("\t %12.8f \t %12.8f \n", real(element), imag(element))
	}
}

func fourier(input []complex128) (output []complex128) {
	var n int = len(input)
	var outSlice []complex128

	for i, _ := range input {
		var sumReal = 0.0
		var sumImag = 0.0

		for t, _ := range input {
			var angle = 2 * math.Pi * float64(i) * float64(t) / float64(n)
			sumReal += real(input[t])*math.Cos(float64(angle)) + imag(input[t])*math.Sin(float64(angle))
			sumImag += -real(input[t])*math.Sin(float64(angle)) + imag(input[t])*math.Cos(float64(angle))
		}
		outSlice = append(outSlice, complex(sumReal, sumImag))
	}
	return outSlice
}