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# scipy.signal.lfiltic

`scipy.signal.``lfiltic`(b, a, y, x=None)

  Construct initial conditions for lfilter.

  Given a linear filter (b, a) and initial conditions on the output y and the input x, return the initial conditions on the state vector zi which is used by `lfilter` to generate the output given the input.

  Parameters: | b : array_like Linear filter term. a : array_like Linear filter term. y : array_like Initial conditions. If `N = len(a) - 1`, then `y = {y[-1], y[-2], ..., y[-N]}`. If y is too short, it is padded with zeros. x : array_like, optional Initial conditions. If `M = len(b) - 1`, then `x = {x[-1], x[-2], ..., x[-M]}`. If x is not given, its initial conditions are assumed zero. If x is too short, it is padded with zeros.
  Returns: | zi : ndarray The state vector `zi = {z_0[-1], z_1[-1], ..., z_K-1[-1]}`, where `K = max(M, N)`.

  See also

  `lfilter`, `lfilter_zi`