# compute DFT
fft_x = fft(window)
l = len(fft_x)
freq = fftfreq(l, 1.0/20)           # matching vector of frequencies
fft_x_shifted = fftshift(fft_x)     # shift DC component
half_l = ceil(l/2.0)
# fold negative frequencies and scale
fft_x_half = abs((2.0 / 256) * fft_x[:half_l])            # ===> Normal decisione tree, good precision.
#fft_x_half = abs((2.0 / 256) * fft_x_shifted[:half_l])   # ===> BIG decisione tree, low precision.
freq_half = freq[:half_l]