Matt Knox wrote:

all I can come up with is dumb brute force methods by iterating through all the values. Anyone got any tricks I can use?

import numpy as np def first_masked(m): idx = np.where(m.mask)[0] if len(idx) != 0: return idx[0] else: raise ValueError("no masked data") first_unmasked() is left as an exercise for the reader. -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco