scipy.signal.findfreqs

scipy.signal.findfreqs(num, den, N)

Find array of frequencies for computing the response of an analog filter.

Parameters:

num, den : array_like, 1-D

The polynomial coefficients of the numerator and denominator of the transfer function of the filter or LTI system. The coefficients are ordered from highest to lowest degree.

N : int

The length of the array to be computed.

Returns:

w : (N,) ndarray

A 1-D array of frequencies, logarithmically spaced.

Examples

Find a set of nine frequencies that span the “interesting part” of the frequency response for the filter with the transfer function

H(s) = s / (s^2 + 8s + 25)

>>> from scipy import signal
>>> signal.findfreqs([1, 0], [1, 8, 25], N=9)
array([  1.00000000e-02,   3.16227766e-02,   1.00000000e-01,
         3.16227766e-01,   1.00000000e+00,   3.16227766e+00,
         1.00000000e+01,   3.16227766e+01,   1.00000000e+02])