[Numpy-discussion] feedback request: proposal to add masks to the core ndarray

Matthew Brett matthew.brett@gmail....
Sat Jun 25 09:31:05 CDT 2011


Hi,

On Sat, Jun 25, 2011 at 3:21 PM, Charles R Harris
<charlesr.harris@gmail.com> wrote:
>
>
> On Sat, Jun 25, 2011 at 5:29 AM, Pierre GM <pgmdevlist@gmail.com> wrote:
>>
>> This thread is getting quite long, innit ?
>> And I think it's getting a tad confusing, because we're mixing two
>> different concepts: missing values and masks.
>> There should be support for missing values in numpy.core, I think we all
>> agree on that.
>> * What's been suggested of adding new dtypes (nafloat, naint) is great, by
>> why not making it the default, then ?
>>
>> * Operations involving a NA (whatever the NA actually is, depending on the
>> dtype of the input) should result in a NA (whatever the NA defined by the
>> outputs dtype). That could be done by overloading the existing ufuncs to
>> support the new dtypes.
>> * There should be some simple methods to retrieve the location of those
>> NAs in an array. Whether we just output the indices or a full boolean array
>> (w/ True for a NA, False for a non-NA or vice-versa) needs to be decided.
>> * We can always re-implement masked arrays to use these NAs in a way which
>> would be consistent with numpy.ma (so as not to confuse existing users of
>> numpy.ma): a mask would be a boolean array with the same shape than the
>> underlying ndarray, with True for NA.
>> Mark, I'd suggest you modify your proposal, making it clearer that it's
>> not to add all of numpy.ma functionalities in the core, but just support
>> these missing values. Using the term 'mask' should be avoided as much as
>> possible, use a 'missing data' or whatever.
>
> I think he aims to support both.

I don't think Mark is proposing to support both.  He's proposing to
implement only array.mask.

See you,

Matthew


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