[Numpy-discussion] Setting custom dtypes and 1.14

josef.pktd at gmail.com josef.pktd at gmail.com
Mon Jan 29 16:02:39 EST 2018


On Mon, Jan 29, 2018 at 3:44 PM, Benjamin Root <ben.v.root at gmail.com> wrote:

> I <3 structured arrays. I love the fact that I can access data by row and
> then by fieldname, or vice versa. There are times when I need to pass just
> a column into a function, and there are times when I need to process things
> row by row. Yes, pandas is nice if you want the specialized indexing
> features, but it becomes a bear to deal with if all you want is normal
> indexing, or even the ability to easily loop over the dataset.
>

I don't think there is a doubt that structured arrays, arrays with
structured dtypes, are a useful container. The question is whether they
should be more or the foundation for more.

For example, computing a mean, or reduce operation, over numeric element
("columns"). Before padded views it was possible to index by selecting the
relevant "columns" and view them as standard array. With padded views that
breaks and AFAICS, there is no way in numpy 1.14.0 to compute a mean of
some "columns". (I don't have numpy 1.14 to try or find a workaround, like
maybe looping over all relevant columns.)

Josef





>
> Cheers!
> Ben Root
>
> On Mon, Jan 29, 2018 at 3:24 PM, <josef.pktd at gmail.com> wrote:
>
>>
>>
>> On Mon, Jan 29, 2018 at 2:55 PM, Stefan van der Walt <
>> stefanv at berkeley.edu> wrote:
>>
>>> On Mon, 29 Jan 2018 14:10:56 -0500, josef.pktd at gmail.com wrote:
>>>
>>>> Given that there is pandas, xarray, dask and more, numpy could as well
>>>> drop
>>>> any pretense of supporting dataframe_likes. Or, adjust the recfunctions
>>>> so
>>>> we can still work dataframe_like with structured
>>>> dtypes/recarrays/recfunctions.
>>>>
>>>
>>> I haven't been following the duckarray discussion carefully, but could
>>> this be an opportunity for a dataframe protocol, so that we can have
>>> libraries ingest structured arrays, record arrays, pandas dataframes,
>>> etc. without too much specialized code?
>>>
>>
>> AFAIU while not being in the data handling area, pandas defines the
>> interface and other libraries provide pandas compatible interfaces or
>> implementations.
>>
>> statsmodels currently still has recarray support and usage. In some
>> interfaces we support pandas, recarrays and plain arrays, or anything where
>> asarray works correctly.
>>
>> But recarrays became messy to support, one rewrite of some functions last
>> year converts recarrays to pandas, does the manipulation and then converts
>> back to recarrays.
>> Also we need to adjust our recarray usage with new numpy versions. But
>> there is no real benefit because I doubt that statsmodels still has any
>> recarray/structured dtype users. So, we only have to remove our own uses in
>> the datasets and unit tests.
>>
>> Josef
>>
>>
>>
>>>
>>> Stéfan
>>>
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>>
>>
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>
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