# endolith/scipy forked from scipy/scipy

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 __all__ = ['fftshift', 'ifftshift', 'fftfreq', 'rfftfreq'] from numpy import arange 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 Parameters ---------- n : int Window length. d : scalar, optional Sample spacing. Default is 1. Returns ------- out : ndarray The array of length `n`, containing the sample frequencies. Examples -------- >>> from scipy import fftpack >>> sig = np.array([-2, 8, 6, 4, 1, 0, 3, 5], dtype=float) >>> sig_fft = fftpack.rfft(sig) >>> n = sig_fft.size >>> timestep = 0.1 >>> freq = fftpack.rfftfreq(n, d=timestep) >>> freq array([ 0. , 1.25, 1.25, 2.5 , 2.5 , 3.75, 3.75, 5. ]) """ if not isinstance(n, int) or n < 0: raise ValueError("n = %s is not valid. n must be a nonnegative integer." % n) return (arange(1, n + 1, dtype=int) // 2) / float(n * d)
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