def _iter_frequencies(q, frange, mismatch, dur):
    """Iterate over the frequencies of this 'QPlane'

    Parameters
    ----------
    q:
        q value
    frange: 'list'
        upper and lower bounds of frequency range
    mismatch:
        percentage of desired fractional mismatch
    dur:
        duration of timeseries in seconds

    Returns
    -------
    frequencies:
        Q-Tile frequency
    """
    # work out how many frequencies we need
    minf, maxf = frange
    fcum_mismatch = log(float(maxf) / minf) * (2 + q**2)**(1/2.) / 2.
    nfreq = int(max(1, ceil(fcum_mismatch / deltam_f(mismatch))))
    fstep = fcum_mismatch / nfreq
    fstepmin = 1. / dur
    # for each frequency, yield a QTile
    for i in xrange(nfreq):
        yield (float(minf) *
               exp(2 / (2 + q**2)**(1/2.) * (i + .5) * fstep) //
               fstepmin * fstepmin)
    raise StopIteration()
Iterate over the frequencies of this 'QPlane'

    Parameters
    ----------
    q:
        q value
    frange: 'list'
        upper and lower bounds of frequency range
    mismatch:
        percentage of desired fractional mismatch
    dur:
        duration of timeseries in seconds

    Returns
    -------
    frequencies:
        Q-Tile frequency