[Numpy-discussion] Quaternion data type

David Cournapeau cournape at gmail.com
Sun May 6 03:56:20 EDT 2012

On Sat, May 5, 2012 at 9:43 PM, Mark Wiebe <mwwiebe at gmail.com> wrote:

> On Sat, May 5, 2012 at 1:06 PM, Charles R Harris <
> charlesr.harris at gmail.com> wrote:
>> On Sat, May 5, 2012 at 11:19 AM, Mark Wiebe <mwwiebe at gmail.com> wrote:
>>> On Sat, May 5, 2012 at 11:55 AM, Charles R Harris <
>>> charlesr.harris at gmail.com> wrote:
>>>> On Sat, May 5, 2012 at 5:27 AM, Tom Aldcroft <
>>>> aldcroft at head.cfa.harvard.edu> wrote:
>>>>> On Fri, May 4, 2012 at 11:44 PM, Ilan Schnell <ischnell at enthought.com>
>>>>> wrote:
>>>>> > Hi Chuck,
>>>>> >
>>>>> > thanks for the prompt reply.  I as curious because because
>>>>> > someone was interested in adding
>>>>> http://pypi.python.org/pypi/Quaternion
>>>>> > to EPD, but Martin and Mark's implementation of quaternions
>>>>> > looks much better.
>>>>> Hi -
>>>>> I'm a co-author of the above mentioned Quaternion package.  I agree
>>>>> the numpy_quaternion version would be better, but if there is no
>>>>> expectation that it will move forward I can offer to improve our
>>>>> Quaternion.  A few months ago I played around with making it accept
>>>>> arbitrary array inputs (with similar shape of course) to essentially
>>>>> vectorize the transformations.  We never got around to putting this in
>>>>> a release because of a perceived lack of interest / priorities... If
>>>>> this would be useful then let me know.
>>>> Would you be interested in carrying Martin's package forward? I'm not
>>>> opposed to having quaternions in numpy/scipy but there needs to be someone
>>>> to push it and deal with problems if they come up. Martin's package
>>>> disappeared in large part because Martin disappeared. I'd also like to hear
>>>> from Mark about other aspects, as there was also a simple rational user
>>>> type proposed that we were looking to put in as an extension 'test' type.
>>>> IIRC, there were some needed fixes to Numpy, some of which were postponed
>>>> in favor of larger changes. User types is one of the things we want ot get
>>>> fixed up.
>>> I kind of like the idea of there being a package, separate from numpy,
>>> which collects these dtypes together. To start, the quaternion and the
>>> rational type could go in it, and eventually I think it would be nice to
>>> move datetime64 there as well. Maybe it could be called numpy-dtypes, or
>>> would a more creative name be better?
>> I'm trying to think about how that would be organized. We could create a
>> new repository, numpy-user-types (numpy-extension-types), under the numpy
>> umbrella. It would need documents and such as well as someone interested in
>> maintaining it and making releases. A branch in the numpy repository
>> wouldn't work since we would want to rebase it regularly. It could maybe go
>> in scipy but a new package would need to be created there and it feels too
>> distant from numpy for such basic types as datetime.
>> Do you have thoughts about the details?
> Another repository under the numpy umbrella would best fit what I'm
> imagining, yes. I would imagine it as a package of additional types that
> aren't the core ones, but that many people would probably want to install.
> It would also be a way to continually exercise the type extension system,
> to make sure it doesn't break. It couldn't be a branch of numpy, rather a
> collection of additional dtypes and associated useful functions.

I would be in favor of this as well. We could start the repository by
having one "trivial" dtype that would serve as an example. That's something
I have been interested in, I can lock a couple of hours / week to help this

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