macf.py 文件源码

def _get_acf_peakheights(lags, acf, npeaks=20, searchinterval=1):
    '''This calculates the relative peak heights for first npeaks in ACF.

    Usually, the first peak or the second peak (if its peak height > first peak)
    corresponds to the correct lag. When we know the correct lag, the period is
    then:

    bestperiod = time[lags == bestlag] - time[0]

    '''

    maxinds = argrelmax(acf, order=searchinterval)[0]
    maxacfs = acf[maxinds]
    maxlags = lags[maxinds]
    mininds = argrelmin(acf, order=searchinterval)[0]
    minacfs = acf[mininds]
    minlags = lags[mininds]

    relpeakheights = np.zeros(npeaks)
    relpeaklags = np.zeros(npeaks,dtype=np.int64)
    peakindices = np.zeros(npeaks,dtype=np.int64)

    for peakind, mxi in enumerate(maxinds[:npeaks]):

        # check if there are no mins to the left
        # throw away this peak because it's probably spurious
        # (FIXME: is this OK?)
        if np.all(mxi < mininds):
            continue

        leftminind = mininds[mininds < mxi][-1] # the last index to the left
        rightminind = mininds[mininds > mxi][0] # the first index to the right
        relpeakheights[peakind] = (
            acf[mxi] - (acf[leftminind] + acf[rightminind])/2.0
        )
        relpeaklags[peakind] = lags[mxi]
        peakindices[peakind] = peakind

    # figure out the bestperiod if possible
    if relpeakheights[0] > relpeakheights[1]:
        bestlag = relpeaklags[0]
        bestpeakheight = relpeakheights[0]
        bestpeakindex = peakindices[0]
    else:
        bestlag = relpeaklags[1]
        bestpeakheight = relpeakheights[1]
        bestpeakindex = peakindices[1]

    return {'maxinds':maxinds,
            'maxacfs':maxacfs,
            'maxlags':maxlags,
            'mininds':mininds,
            'minacfs':minacfs,
            'minlags':minlags,
            'relpeakheights':relpeakheights,
            'relpeaklags':relpeaklags,
            'peakindices':peakindices,
            'bestlag':bestlag,
            'bestpeakheight':bestpeakheight,
            'bestpeakindex':bestpeakindex}