[Numpy-discussion] using the same vocabulary for missing value ideas

[Christopher Jordan-Squire]

On Wed, Jul 6, 2011 at 5:38 PM, Benjamin Root <ben.root at ou.edu> wrote:

> On Wednesday, July 6, 2011, Christopher Jordan-Squire <cjordan1 at uw.edu>
> wrote:
> >
> >
> > On Wed, Jul 6, 2011 at 5:03 PM, Benjamin Root <ben.root at ou.edu> wrote:
> >
> > On Wednesday, July 6, 2011, Dag Sverre Seljebotn
> > <d.s.seljebotn at astro.uio.no> wrote:
> >> On 07/06/2011 08:25 PM, Christopher Barker wrote:
> >>> Mark Wiebe wrote:
> >>>> 1) NA vs IGNORE and bitpattern vs mask are completely independent. Any
> >>>> combination of NA as bitpattern, NA as mask, IGNORE as bitpattern, and
> >>>> IGNORE as mask are reasonable.
> >>>
> >>> Is this really true? if you use a bitpattern for IGNORE, haven't you
> >>> just lost the ability to get the original value back if you want to
> stop
> >>> ignoring it? Maybe that's not inherent to what an IGNORE means, but it
> >>> seems pretty key to me.
> >>
> >> There's the question of how reductions treats the value. IIUC, IGNORE as
> >> bitpattern would imply that reductions treat the value as 0, which is a
> >> question orthogonal to whether the value can possibly be unmasked or
> not.
> >>
> >> Dag Sverre
> >>
> >
> > Just because we are trying to be exact here, the reductions would
> > treat IGNORE as the operation's identity.  Therefore, for addition, it
> > would be treated like 0, but for multiplication, it is treated like a
> > 1.
> >
> > Ben Root
> >
> > Yes. But, as discussed on another thread, that can lead to unexpected
> results when it's propagated through several operations.
> >
> >
>
> If you are talking about means, for example, then the count is
> adjusted before dividing.  It is like they never existed. Same with
> standard deviation. Of course, there are issues with having fewer
> samples, but that isn't a problem caused by the underlying concept of
> skipping elements.
>
> As long as the underlying mathematical support for array math is still
> valid, I am not certain what the issue is.  Matrix math on the other
> hand...
>
>
Ah, I see. I misunderstood the class of operations you were discussing.

-Chris Jordan-Squire



> Ben Root
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