numpy.fft.fftshift — NumPy v1.13 Manual (original) (raw)
numpy.fft. fftshift(x, axes=None)[source]¶
Shift the zero-frequency component to the center of the spectrum.
This function swaps half-spaces for all axes listed (defaults to all). Note that y[0] is the Nyquist component only if len(x) is even.
| Parameters: | x : array_like Input array. axes : int or shape tuple, optional Axes over which to shift. Default is None, which shifts all axes. |
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| Returns: | y : ndarray The shifted array. |
Examples
freqs = np.fft.fftfreq(10, 0.1) freqs array([ 0., 1., 2., 3., 4., -5., -4., -3., -2., -1.]) np.fft.fftshift(freqs) array([-5., -4., -3., -2., -1., 0., 1., 2., 3., 4.])
Shift the zero-frequency component only along the second axis:
freqs = np.fft.fftfreq(9, d=1./9).reshape(3, 3) freqs array([[ 0., 1., 2.], [ 3., 4., -4.], [-3., -2., -1.]]) np.fft.fftshift(freqs, axes=(1,)) array([[ 2., 0., 1.], [-4., 3., 4.], [-1., -3., -2.]])