'Set UT1-UTC source flag for entries in IERS table'

def ut1_utc_source(self, i):

    ut1flag = self[u'UT1Flag'][i]
    source = (np.ones_like(i) * FROM_IERS_B)
    source[(ut1flag == u'I')] = FROM_IERS_A
    source[(ut1flag == u'P')] = FROM_IERS_A_PREDICTION
    return source
