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__all__ = ['fftshift', 'ifftshift', 'fftfreq', 'rfftfreq']
from numpy import array
from numpy.fft.helper import fftshift, ifftshift, fftfreq
def rfftfreq(n, d=1.0):
"""DFT sample frequencies (for usage with rfft, irfft).
The returned float array contains the frequency bins in
cycles/unit (with zero at the start) given a window length n and a
sample spacing d:
f = [0,1,1,2,2,...,n/2-1,n/2-1,n/2]/(d*n) if n is even
f = [0,1,1,2,2,...,n/2-1,n/2-1,n/2,n/2]/(d*n) if n is odd
"""
if not isinstance(n, int) or n < 0:
raise ValueError("n = %s is not valid. n must be a nonnegative integer." % n)
return (array(range(1,n+1),dtype=int)//2)/float(n*d)
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