Discreet Fourier Transform in Python

dct.py

"""Based on Javascript from
http://madebyevan.com/dft/

This may be wrong, but seems to do what I'd expect...
"""

from __future__ import division
import sys
import math

def ascii_plot(vals, width = 40):
    mi = min(vals)
    ma = max(vals)
    print " " * (int(((0 - mi)/ma) * width)-1) + "0"
    for x in vals:
        print "#" * int((((x-mi) / ma) * width))

funcextent = 8
samplecount = 2**int(sys.argv[1])

def sample_func(f):
    spatialX = [None for x in range(samplecount)]
    spatialY = [None for x in range(samplecount)]
    for i in range(samplecount):
        spatialX[i] = (i / samplecount*2-1) * funcextent
        spatialY[i] = f(spatialX[i])

    return (spatialX, spatialY)

def box(x):
    return int(x > -1) and int(x < 1)

def discreet_fourier_transform(spatialX, spatialY):
    freqRealX = spatialX
    freqImagX = spatialX
    freqRealY = [None for x in range(samplecount)]
    freqImagY = [None for x in range(samplecount)]

    for i in range(samplecount):
        ii = (i+samplecount/2) % samplecount
        ii = int(ii)
        freqRealY[ii] = freqImagY[ii] = 0
        for j in range(samplecount):
            jj = (j+samplecount / 2) % samplecount
            jj = int(jj)
            freqRealY[ii] += spatialY[jj] * math.cos(-2 * math.pi * i * j / samplecount)
            freqImagY[ii] += spatialY[jj] * math.sin(-2 * math.pi * i * j / samplecount)

    #ascii_plot(freqRealY)

spatialX, spatialY = sample_func(box)
discreet_fourier_transform(spatialX, spatialY)