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# scipy.signal.iirfilter

`scipy.signal.``iirfilter`(N, Wn, rp=None, rs=None, btype='band', analog=0, ftype='butter', output='ba')

  IIR digital and analog filter design given order and critical points.

  Design an Nth order lowpass digital or analog filter and return the filter coefficients in (B,A) (numerator, denominator) or (Z,P,K) form.

  Parameters: | N – the order of the filter. : Wn – a scalar or length-2 sequence giving the critical frequencies. : rp, rs – For chebyshev and elliptic filters provides the maximum ripple : in the passband and the minimum attenuation in the stop band. btype – the type of filter (lowpass, highpass, bandpass, or bandstop). : analog – non-zero to return an analog filter, otherwise : a digital filter is returned. ftype – the type of IIR filter (Butterworth, Cauer (Elliptic), : Bessel, Chebyshev1, Chebyshev2) output – ‘ba’ for (b,a) output, ‘zpk’ for (z,p,k) output. : SEE ALSO butterord, cheb1ord, cheb2ord, ellipord :

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