On Wed, Nov 21, 2012 at 9:22 PM, Olivier Delalleau <[email protected]> wrote: > Current behavior looks sensible to me. I personally would prefer no warning > but I think it makes sense to have one as it can be helpful to detect issues > faster.
I agree that nan should be the correct answer. (I gave up trying to define a default for 0/0 in scipy.stats ttests.) some funnier cases >>> np.var([1], ddof=1) 0.0 >>> np.var([1], ddof=5) -0 >>> np.var([1,2], ddof=5) -0.16666666666666666 >>> np.std([1,2], ddof=5) nan But maybe my numpy is too old on my open interpreter >>> np.__version__ '1.5.1' Josef > > -=- Olivier > > 2012/11/21 Charles R Harris <[email protected]> >> >> What should be the value of the mean, var, and std of empty arrays? >> Currently >> >> In [12]: a >> Out[12]: array([], dtype=int64) >> >> In [13]: a.mean() >> Out[13]: nan >> >> In [14]: a.std() >> Out[14]: nan >> >> In [15]: a.var() >> Out[15]: nan >> >> I think the nan comes from 0/0. All of these also raise warnings the first >> time they are called. >> >> Chuck >> >> >> _______________________________________________ >> NumPy-Discussion mailing list >> [email protected] >> http://mail.scipy.org/mailman/listinfo/numpy-discussion >> > > > _______________________________________________ > NumPy-Discussion mailing list > [email protected] > http://mail.scipy.org/mailman/listinfo/numpy-discussion > _______________________________________________ NumPy-Discussion mailing list [email protected] http://mail.scipy.org/mailman/listinfo/numpy-discussion
