Hi, On Tue, Jun 28, 2011 at 4:06 PM, Nathaniel Smith <n...@pobox.com> wrote: ... > (You might think, what difference does it make if you *can* unmask an > item? Us missing data folks could just ignore this feature. But: > whatever we end up implementing is something that I will have to > explain over and over to different people, most of them not > particularly sophisticated programmers. And there's just no sensible > way to explain this idea that if you store some particular value, then > it replaces the old value, but if you store NA, then the old value is > still there.
Ouch - yes. No question, that is difficult to explain. Well, I think the explanation might go like this: "Ah, yes, well, that's because in fact numpy records missing values by using a 'mask'. So when you say `a[3] = np.NA', what you mean is, 'a._mask = np.ones(a.shape, np.dtype(bool); a._mask[3] = False`" Is that fair? See you, Matthew _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion