[Numpy-discussion] proposal: min, max of complex should give warning
ndbecker2 at gmail.com
Tue Dec 31 11:45:08 EST 2013
Ralf Gommers wrote:
> On Tue, Dec 31, 2013 at 4:52 PM, Neal Becker <ndbecker2 at gmail.com> wrote:
>> Cera, Tim wrote:
>> > I don't work with complex numbers, but just sampling what others do:
>> > Python: no ordering, results in TypeError
>> > Matlab: sorts by magnitude
>> > http://www.mathworks.com/help/matlab/ref/sort.html
>> > R: sorts first by real, then by imaginary
>> > http://stat.ethz.ch/R-manual/R-patched/library/base/html/sort.html
>> > Numpy: sorts first by real, then by imaginary (the documentation link
>> > below calls this sort 'lexicographical' which I don't think is
>> > correct)
>> > http://docs.scipy.org/doc/numpy/reference/generated/numpy.sort.html
>> > I would think that the Matlab sort might be more useful, but easy
>> > enough by using the absolute value.
>> > I think what Numpy does is normal enough to not justify a warning, but
>> > leave this to others because as I pointed out in the beginning I don't
>> > work with complex numbers.
>> > Kindest regards,
>> > Tim
>> But I'm not proposing to change numpy's result, which I'm sure would raise
>> objections. I'm just asking to give a warning, because I think in most
>> this is actually a mistake on the user's part. Just like the warning
>> given when complex data are truncated to real part.
> Keep in mind that warnings can be highly annoying. If you're a user who
> uses this functionality regularly (and you know what you're doing), then
> you're going to be very unhappy to have to wrap each function call in:
> olderr = np.seterr(all='ignore')
> or in:
> with warnings.catch_warnings():
> warnings.filterwarnings('ignore', ...)
> The actual behavior isn't documented now it looks like, so that should be
> done. In the Notes section of max/min probably.
> As for your proposal, it would be good to know if adding a warning would
> actually catch any bugs. For the truncation warning it caught several in
> scipy and other libs IIRC.
I tripped over it yesterday, which is what prompted my suggestion.
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