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

Charles R Harris charlesr.harris@gmail....
Sat Jun 25 09:46:18 CDT 2011


On Sat, Jun 25, 2011 at 8:31 AM, Matthew Brett <matthew.brett@gmail.com>wrote:

> 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.
>
>
I think you are confusing function with implementation. If you look at the
current NEP, it does NA but does so by using masks behind the scene in a
transparent manner.

Chuck
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