[Numpy-discussion] two questions about `choose`

[Kevin Sheppard]

Oh. I answered thinking about choice and not choose. Please ignore both
parts.

On Sun, Apr 18, 2021, 17:56 Robert Kern <robert.kern at gmail.com> wrote:

> On Sat, Apr 17, 2021 at 4:28 PM Kevin Sheppard <kevin.k.sheppard at gmail.com>
> wrote:
>
>> 1. I suppose it only uses the (Native int or int64) dtype since each one
>> would need a code path to run quickly.
>>
>> 2. I would describe this a a bug. I think sequences are converted to
>> arrays and in this case the conversion is not returning a 2 element object
>> array but expanding and then concatenation.
>>
>
> No, it's broadcasting the two to a common shape, as documented.
> https://numpy.org/doc/stable/reference/generated/numpy.choose.html
>
>
>> E.g.,
>>> a = a = (0,1,1,0,0,0,1,1)  #binary array
>>> np.choose(a, (0,range(8))     #array([0, 1, 2, 0, 0, 0, 6, 7])
>>>
>>
> This is equivalent to `np.choose(a, (np.zeros(8, dtype=int), range(8)))`
>
> --
> Robert Kern
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