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# scipy.signal.iirdesign

`scipy.signal.``iirdesign`(wp, ws, gpass, gstop, analog=0, ftype='ellip', output='ba')

  Complete IIR digital and analog filter design.

  Given passband and stopband frequencies and gains construct an analog or digital IIR filter of minimum order for a given basic type. Return the output in numerator, denominator (‘ba’) or pole-zero (‘zpk’) form.

  Parameters : | wp, ws : float Passband and stopband edge frequencies, normalized from 0 to 1 (1 corresponds to pi radians / sample). For example: Lowpass: wp = 0.2, ws = 0.3 Highpass: wp = 0.3, ws = 0.2 Bandpass: wp = [0.2, 0.5], ws = [0.1, 0.6] Bandstop: wp = [0.1, 0.6], ws = [0.2, 0.5] gpass : float The maximum loss in the passband (dB). gstop : float The minimum attenuation in the stopband (dB). analog : int, optional Non-zero to design an analog filter (in this case wp and ws are in radians / second). ftype : str, optional The type of IIR filter to design: elliptic : ‘ellip’ Butterworth : ‘butter’, Chebyshev I : ‘cheby1’, Chebyshev II: ‘cheby2’, Bessel : ‘bessel’ output : [‘ba’, ‘zpk’], optional Type of output: numerator/denominator (‘ba’) or pole-zero (‘zpk’). Default is ‘ba’.
  Returns : | b, a : : Numerator and denominator of the IIR filter. Only returned if `output='ba'`. z, p, k : Zeros, poles, and gain of the IIR filter. Only returned if ``output=’zpk’``. :

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