[Numpy-discussion] linspace handling of extra return

[Jaime Fernández del Río]

On Tue, Jan 13, 2015 at 7:23 AM, Benjamin Root <ben.root at ou.edu> wrote:

> Oh, wow. I never noticed that before. Yeah, if I state that retstep=True,
> then I am coding my handling to expect two values to be returned, not 1. I
> think it should be nan, but I could also agree with zero. It should
> definitely remain a float value, though.
>

NaN it is then: the change and supporting tests are now part of gh-5446.

Jaime


>
> Cheers!
> Ben Root
>
> On Tue, Jan 13, 2015 at 10:15 AM, Jaime Fernández del Río <
> jaime.frio at gmail.com> wrote:
>
>> While working on something else, I realized that linspace is not handling
>> requests for returning the sampling spacing consistently:
>>
>> >>> np.linspace(0, 1, 3, retstep=True)
>> (array([ 0. ,  0.5,  1. ]), 0.5)
>> >>> np.linspace(0, 1, 1, retstep=True)
>> array([ 0.])
>> >>> np.linspace(0, 1, 0, retstep=True)
>> array([], dtype=float64)
>>
>> Basically, retstep is ignored if the number of samples is 0 or 1. One
>> could argue that it makes sense, because those sequences do not have a
>> spacing defined. But at the very least it should be documented as doing so,
>> and the following inconsistency removed:
>>
>> >>> np.linspace(0, 1, 1, endpoint=True, retstep=True)
>> array([ 0.])
>> >>> np.linspace(0, 1, 1, endpoint=False, retstep=True)
>> (array([ 0.]), 1.0)
>>
>> I am personally inclined to think that if a step is requested, then a
>> step should be returned, and if it cannot be calculated in a reasonable
>> manner, then a placeholder such as None, nan, 0 or stop - start should be
>> returned.
>>
>> What does the collective wisdom think is the best approach for this?
>>
>> Jaime
>>
>> --
>> (\__/)
>> ( O.o)
>> ( > <) Este es Conejo. Copia a Conejo en tu firma y ayúdale en sus planes
>> de dominación mundial.
>>
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>
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-- 
(\__/)
( O.o)
( > <) Este es Conejo. Copia a Conejo en tu firma y ayúdale en sus planes
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