Module « scipy.signal »

Fonction sosfilt_zi - module scipy.signal

Signature de la fonction sosfilt_zi

def sosfilt_zi(sos) 

Description

sosfilt_zi.__doc__

    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`.

    >>> 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()