mars.tensor.fft.fftshift#

mars.tensor.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 tensor.
axes (int or shape tuple, optional) – Axes over which to shift. Default is None, which shifts all axes.

Returns

y – The shifted tensor.

Return type

Tensor

See also

ifftshift: The inverse of fftshift.

Examples

>>> import mars.tensor as mt

>>> freqs = mt.fft.fftfreq(10, 0.1)
>>> freqs.execute()
array([ 0.,  1.,  2.,  3.,  4., -5., -4., -3., -2., -1.])
>>> mt.fft.fftshift(freqs).execute()
array([-5., -4., -3., -2., -1.,  0.,  1.,  2.,  3.,  4.])

Shift the zero-frequency component only along the second axis:

>>> freqs = mt.fft.fftfreq(9, d=1./9).reshape(3, 3)
>>> freqs.execute()
array([[ 0.,  1.,  2.],
       [ 3.,  4., -4.],
       [-3., -2., -1.]])
>>> mt.fft.fftshift(freqs, axes=(1,)).execute()
array([[ 2.,  0.,  1.],
       [-4.,  3.,  4.],
       [-1., -3., -2.]])