I have picked up a strange limit to np.in1d(): ---------- b Out[100]: array(['2007-01-01T02:30:00+0200', '2007-01-01T03:00:00+0200', '2007-01-01T03:30:00+0200', ..., '2008-01-01T01:00:00+0200', '2008-01-01T01:30:00+0200', '2008-01-01T02:00:00+0200'], dtype='datetime64[s]') b.shape Out[101]: (17520,) a = b[0:42] np.in1d(b,a) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/grove/<ipython-input-103-a7d9d12b1353> in <module>() ----> 1 np.in1d(b,a) /usr/local/lib/python2.6/dist-packages/numpy/lib/arraysetops.pyc in in1d(ar1, ar2, assume_unique) 338 # here. The values from the first array should always come before 339 # the values from the second array. --> 340 order = ar.argsort(kind='mergesort') 341 sar = ar[order] 342 equal_adj = (sar[1:] == sar[:-1]) TypeError: requested sort not available for type But this works: a = b[0:41] np.in1d(b,a) Out[105]: array([ True, True, True, ..., False, False, False], dtype=bool) --------- In other words the limit seems to be 41 elements for a. Is this a bug or am I getting something wrong? Grové