On Thu, Oct 3, 2013 at 1:11 PM, Nathaniel Smith <n...@pobox.com> wrote:
> On Thu, Oct 3, 2013 at 7:59 PM, Charles R Harris > <charlesr.har...@gmail.com> wrote: > > > > <snip> > > > >> > >> Please, no. It's another thing to remember and another way to shoot > >> yourself in the foot and introduce casual bugs. > >> > >> FWIW, my vote is to raise an error or return a nan, which will likely > >> eventually raise an error. If I have all nans, it's usually the case > >> that something's off, and I'd like to know sooner rather than later. > >> > > > > Here is what I have currently implemented. First, define an AllNanError > > > > class AllNanError(ValueError): > > def __init__(self, msg, result): > > ValueError.__init__(self, msg) > > self.result = result > > > > For nanmax/nanmin/nanargmax/nanargmin this error is raised for all-nan > axis > > and the result is attached. The exception can then be caught and the > result > > examined. A ValueError is what amax, amin return for empty arrays. > > > > For nanmax/nanmin the result for an empty slice is nan. For > > argnanmax/argnanmin the result of an empty slice is -1, which is easier > to > > read and remember than intp.min. A ValueError is what argmin, argmax > > currently return for empty arrays. Note that both of these functions can > > give wrong results if they contain some min/max values respectively. > That is > > an old bug and I haven't fixed it. > > > > The nanmean/nanvar/nanstd functions currently raise a warning for all-nan > > slices and the result for such is nan. These could also be made to raise > an > > error. > > > > Thoughts? > > Is this intended for 1.8 or master? > I was thinking both. The nanarg* functions are changing behavior anyway, so might as well get it all done in 1.8. I also think there will need to be an rc2 in anycase. the current non-nan aware mean/var/std only raise warnings on insufficient degrees of freedom and return nan. That's a bit of a change, they used to return nans, negative numbers, and other things in that situation. Chuck
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