def iirdesign(wp, ws, gpass, gstop, analog=False, 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'), pole-zero ('zpk') or second order
    sections ('sos') form.

    Parameters
    ----------
    wp, ws : float
        Passband and stopband edge frequencies.
        For digital filters, these are normalized from 0 to 1, where 1 is the
        Nyquist frequency, pi radians/sample.  (`wp` and `ws` are thus in
        half-cycles / 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]

        For analog filters, `wp` and `ws` are angular frequencies (e.g. rad/s).

    gpass : float
        The maximum loss in the passband (dB).
    gstop : float
        The minimum attenuation in the stopband (dB).
    analog : bool, optional
        When True, return an analog filter, otherwise a digital filter is
        returned.
    ftype : str, optional
        The type of IIR filter to design:

            - Butterworth   : 'butter'
            - Chebyshev I   : 'cheby1'
            - Chebyshev II  : 'cheby2'
            - Cauer/elliptic: 'ellip'
            - Bessel/Thomson: 'bessel'

    output : {'ba', 'zpk', 'sos'}, optional
        Type of output:  numerator/denominator ('ba'), pole-zero ('zpk'), or
        second-order sections ('sos'). Default is 'ba'.

    Returns
    -------
    b, a : ndarray, ndarray
        Numerator (`b`) and denominator (`a`) polynomials of the IIR filter.
        Only returned if ``output='ba'``.
    z, p, k : ndarray, ndarray, float
        Zeros, poles, and system gain of the IIR filter transfer
        function.  Only returned if ``output='zpk'``.
    sos : ndarray
        Second-order sections representation of the IIR filter.
        Only returned if ``output=='sos'``.

    See Also
    --------
    butter : Filter design using order and critical points
    cheby1, cheby2, ellip, bessel
    buttord : Find order and critical points from passband and stopband spec
    cheb1ord, cheb2ord, ellipord
    iirfilter : General filter design using order and critical frequencies

    Notes
    -----
    The ``'sos'`` output parameter was added in 0.16.0.
    """
    try:
        ordfunc = filter_dict[ftype][1]
    except KeyError:
        raise ValueError("Invalid IIR filter type: %s" % ftype)
    except __HOLE__:
        raise ValueError(("%s does not have order selection. Use "
                          "iirfilter function.") % ftype)

    wp = atleast_1d(wp)
    ws = atleast_1d(ws)
    band_type = 2 * (len(wp) - 1)
    band_type += 1
    if wp[0] >= ws[0]:
        band_type += 1

    btype = {1: 'lowpass', 2: 'highpass',
             3: 'bandstop', 4: 'bandpass'}[band_type]

    N, Wn = ordfunc(wp, ws, gpass, gstop, analog=analog)
    return iirfilter(N, Wn, rp=gpass, rs=gstop, analog=analog, btype=btype,
                     ftype=ftype, output=output)
dataset/ETHPy150Open scipy/scipy/scipy/signal/filter_design.py/iirdesign