On Wed, Jul 6, 2011 at 5:38 PM, Benjamin Root <[email protected]> wrote:
> On Wednesday, July 6, 2011, Christopher Jordan-Squire <[email protected]> > wrote: > > > > > > On Wed, Jul 6, 2011 at 5:03 PM, Benjamin Root <[email protected]> wrote: > > > > On Wednesday, July 6, 2011, Dag Sverre Seljebotn > > <[email protected]> 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 > _______________________________________________ > NumPy-Discussion mailing list > [email protected] > http://mail.scipy.org/mailman/listinfo/numpy-discussion >
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