stats_computation.py 文件源码

def stetsonK(mag, magerr):
    """The variability index K was first suggested by Peter B. Stetson and serves as a 
    measure of the kurtosis of the magnitude distribution. 
    See: (P. B. Stetson, Publications of the Astronomical Society of the Pacific 108, 851 (1996)).

    :param mag: the time-varying intensity of the object. Must be an array.
    :param magerr: photometric error for the intensity. Must be an array.

    :rtype: float
    """

    mag, magerr = remove_bad(mag, magerr)            
    n = np.float(len(mag))
    #mean = meanMag(mag, magerr)
    mean = np.median(mag)

    delta = np.sqrt((n/(n-1.)))*((mag - mean)/magerr)

    stetsonK = ((1./n)*sum(abs(delta)))/(np.sqrt((1./n)*sum(delta**2)))
    return np.nan_to_num(stetsonK)