`numpy.fft:fftfreq`

source: build-install/usr/lib/python3.14/site-packages/numpy/fft/_helper.py :125

Signature

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

Summary

Return the Discrete Fourier Transform sample frequencies.

Extended Summary

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.
device : str, optional: The device on which to place the created array. Default: None. For Array-API interoperability only, so must be "cpu" if passed.
versionadded 2.0.0

Returns

f : ndarray: Array of length n containing the sample frequencies.

Examples

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

✓

Aliases

numpy.fft.fftfreq