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

Charles R Harris charlesr.harris@gmail....
Thu Jun 23 19:21:11 CDT 2011

On Thu, Jun 23, 2011 at 6:00 PM, Nathaniel Smith <njs@pobox.com> wrote:

> On Thu, Jun 23, 2011 at 2:44 PM, Robert Kern <robert.kern@gmail.com>
> wrote:
> > On Thu, Jun 23, 2011 at 15:53, Mark Wiebe <mwwiebe@gmail.com> wrote:
> >> Enthought has asked me to look into the "missing data" problem and how
> NumPy
> >> could treat it better. I've considered the different ideas of adding
> dtype
> >> variants with a special signal value and masked arrays, and concluded
> that
> >> adding masks to the core ndarray appears is the best way to deal with
> the
> >> problem in general.
> >> I've written a NEP that proposes a particular design, viewable here:
> >>
> https://github.com/m-paradox/numpy/blob/cmaskedarray/doc/neps/c-masked-array.rst
> >> There are some questions at the bottom of the NEP which definitely need
> >> discussion to find the best design choices. Please read, and let me know
> of
> >> all the errors and gaps you find in the document.
> >
> > One thing that could use more explanation is how your proposal
> > improves on the status quo, i.e. numpy.ma. As far as I can see, you
> > are mostly just shuffling around the functionality that already
> > exists. There has been a continual desire for something like R's NA
> > values by people who are very familiar with both R and numpy's masked
> > arrays. Both have their uses, and as Nathaniel points out, R's
> > approach seems to be very well-liked by a lot of users. In essence,
> > *that's* the "missing data problem" that you were charged with: making
> > happy the users who are currently dissatisfied with masked arrays. It
> > doesn't seem to me that moving the functionality from numpy.ma to
> > numpy.ndarray resolves any of their issues.
> Speaking as a user who's avoided numpy.ma, it wasn't actually because
> of the behavior I pointed out (I never got far enough to notice it),
> but because I got the distinct impression that it was a "second-class
> citizen" in numpy-land. I don't know if that's true. But I wasn't sure
> how solidly things like interactions between numpy and masked arrays
> worked, or how , and it seemed like it had more niche uses. So it just
> seemed like more hassle than it was worth for my purposes. Moving it
> into the core and making it really solid *would* address these
> issues...
There is some truth to that. The maintainer/creator of masked arrays was
Pierre and he hasn't much time these days. Given that numpy will continue to
advance and add features it is probably best for the masked array facility
to be part of the basic toolset.


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