[Numpy-discussion] Datarray BoF, part2

Keith Goodman kwgoodman@gmail....
Wed Jul 21 14:00:18 CDT 2010


On Wed, Jul 21, 2010 at 11:41 AM, Vincent Davis
<vincent@vincentdavis.net> wrote:
> On Wed, Jul 21, 2010 at 11:08 AM, Keith Goodman <kwgoodman@gmail.com> wrote:
>> On Wed, Jul 21, 2010 at 9:56 AM, John Salvatier
>> <jsalvati@u.washington.edu> wrote:
>>> I don't really know much about this topic, but what about a flag at array
>>> creation time (or whenever you define labels) that says whether valid
>>> indexes will be treated as labels or indexes for that array?
>>
>> It's an interesting idea. My guess is that you'd end up having to
>> check the attribute all the time when writing code:
>>
>> if dar.intaslabel:
>>    dar2 = dar[tickmap(i)]
>> else:
>>    dar2 = dar[i]
>
> Obviously there are several aspects of a labels that need to be
> considered. An important on is if an operation breaks the meaning of
> the labels. I like the idea of tickmap(i) it could have a lot of
> features like grouping... Maybe even work on structure arrays(maybe).
> The flag could connect the tickmap() to the array. Then if an
> operation was performed on the array to would result in the labels no
> longer being meaningful then the flag would change. In this way
> tickmap(i) checks for the flags and each axis could have a flag.
> (I am sure there is lots I am missing)

Each axis currently has a tick map: Axis._tick_dict. From a datarray
you can access it like this:

>> from datarray import DataArray
>> x = DataArray([1,2,3], labels=[('time', ['n1', 'n2', 'n3'])])
>> x.axis.time._tick_dict
   {'n1': 0, 'n2': 1, 'n3': 2}
>> x.axes[0]._tick_dict
   {'n1': 0, 'n2': 1, 'n3': 2}
>> x.axis['time']._tick_dict
   {'n1': 0, 'n2': 1, 'n3': 2}

On a separate note, I think having both axis and axes attribute is
confusing. Would it be possible to only have one of them? Here's a
proposal: http://github.com/fperez/datarray/commit/01b2d3d2082ade38ec89dbca0c070dd4fc9d9ca3#L1R330


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