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Fonction cascade - module scipy.signal

Signature de la fonction cascade

def cascade(hk, J=7) 

Description

cascade.__doc__

    Return (x, phi, psi) at dyadic points ``K/2**J`` from filter coefficients.

    Parameters
    ----------
    hk : array_like
        Coefficients of low-pass filter.
    J : int, optional
        Values will be computed at grid points ``K/2**J``. Default is 7.

    Returns
    -------
    x : ndarray
        The dyadic points ``K/2**J`` for ``K=0...N * (2**J)-1`` where
        ``len(hk) = len(gk) = N+1``.
    phi : ndarray
        The scaling function ``phi(x)`` at `x`:
        ``phi(x) = sum(hk * phi(2x-k))``, where k is from 0 to N.
    psi : ndarray, optional
        The wavelet function ``psi(x)`` at `x`:
        ``phi(x) = sum(gk * phi(2x-k))``, where k is from 0 to N.
        `psi` is only returned if `gk` is not None.

    Notes
    -----
    The algorithm uses the vector cascade algorithm described by Strang and
    Nguyen in "Wavelets and Filter Banks".  It builds a dictionary of values
    and slices for quick reuse.  Then inserts vectors into final vector at the
    end.