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Module « scipy.signal »

Fonction sosfilt_zi - module scipy.signal

Signature de la fonction sosfilt_zi

def sosfilt_zi(sos) 

Description

help(scipy.signal.sosfilt_zi)

Construct initial conditions for sosfilt for step response steady-state.

Compute an initial state `zi` for the `sosfilt` function that corresponds
to the steady state of the step response.

A typical use of this function is to set the initial state so that the
output of the filter starts at the same value as the first element of
the signal to be filtered.

Parameters
----------
sos : array_like
    Array of second-order filter coefficients, must have shape
    ``(n_sections, 6)``. See `sosfilt` for the SOS filter format
    specification.

Returns
-------
zi : ndarray
    Initial conditions suitable for use with ``sosfilt``, shape
    ``(n_sections, 2)``.

See Also
--------
sosfilt, zpk2sos

Notes
-----
.. versionadded:: 0.16.0

Examples
--------
Filter a rectangular pulse that begins at time 0, with and without
the use of the `zi` argument of `scipy.signal.sosfilt`.

>>> import numpy as np
>>> from scipy import signal
>>> import matplotlib.pyplot as plt

>>> sos = signal.butter(9, 0.125, output='sos')
>>> zi = signal.sosfilt_zi(sos)
>>> x = (np.arange(250) < 100).astype(int)
>>> f1 = signal.sosfilt(sos, x)
>>> f2, zo = signal.sosfilt(sos, x, zi=zi)

>>> plt.plot(x, 'k--', label='x')
>>> plt.plot(f1, 'b', alpha=0.5, linewidth=2, label='filtered')
>>> plt.plot(f2, 'g', alpha=0.25, linewidth=4, label='filtered with zi')
>>> plt.legend(loc='best')
>>> plt.show()

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