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Module « scipy.fft »

Fonction fftfreq - module scipy.fft

Signature de la fonction fftfreq

def fftfreq(n, d=1.0, *, xp=None, device=None) 

Description

help(scipy.fft.fftfreq)

Return the Discrete Fourier Transform sample frequencies.

The returned float array `f` contains the frequency bin centers in cycles
per unit of the sample spacing (with zero at the start).  For instance, if
the sample spacing is in seconds, then the frequency unit is cycles/second.

Given a window length `n` and a sample spacing `d`::

  f = [0, 1, ...,   n/2-1,     -n/2, ..., -1] / (d*n)   if n is even
  f = [0, 1, ..., (n-1)/2, -(n-1)/2, ..., -1] / (d*n)   if n is odd

Parameters
----------
n : int
    Window length.
d : scalar, optional
    Sample spacing (inverse of the sampling rate). Defaults to 1.
xp : array_namespace, optional
    The namespace for the return array. Default is None, where NumPy is used.
device : device, optional
    The device for the return array.
    Only valid when `xp.fft.fftfreq` implements the device parameter.
 
Returns
-------
f : ndarray
    Array of length `n` containing the sample frequencies.

Examples
--------
>>> import numpy as np
>>> import scipy.fft
>>> signal = np.array([-2, 8, 6, 4, 1, 0, 3, 5], dtype=float)
>>> fourier = scipy.fft.fft(signal)
>>> n = signal.size
>>> timestep = 0.1
>>> freq = scipy.fft.fftfreq(n, d=timestep)
>>> freq
array([ 0.  ,  1.25,  2.5 , ..., -3.75, -2.5 , -1.25])

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