cupyx.scipy.signal.zoom_fft(x, fn, m=None, *, fs=2, endpoint=False, axis=-1)[source]#

Compute the DFT of x only for frequencies in range fn.

  • x (array) – The signal to transform.

  • fn (array_like) – A length-2 sequence [f1, f2] giving the frequency range, or a scalar, for which the range [0, fn] is assumed.

  • m (int, optional) – The number of points to evaluate. The default is the length of x.

  • fs (float, optional) – The sampling frequency. If fs=10 represented 10 kHz, for example, then f1 and f2 would also be given in kHz. The default sampling frequency is 2, so f1 and f2 should be in the range [0, 1] to keep the transform below the Nyquist frequency.

  • endpoint (bool, optional) – If True, f2 is the last sample. Otherwise, it is not included. Default is False.

  • axis (int, optional) – Axis over which to compute the FFT. If not given, the last axis is used.


out – The transformed signal. The Fourier transform will be calculated at the points f1, f1+df, f1+2df, …, f2, where df=(f2-f1)/m.

Return type


See also


Class that creates a callable partial FFT function.



The defaults are chosen such that signal.zoom_fft(x, 2) is equivalent to fft.fft(x) and, if m > len(x), that signal.zoom_fft(x, 2, m) is equivalent to fft.fft(x, m).

To graph the magnitude of the resulting transform, use:

plot(linspace(f1, f2, m, endpoint=False),
     abs(zoom_fft(x, [f1, f2], m)))

If the transform needs to be repeated, use ZoomFFT to construct a specialized transform function which can be reused without recomputing constants.