A reimplementation of MaskedArray

Tim Hochberg tim.hochberg at ieee.org
Wed Nov 8 13:24:34 CST 2006


A. M. Archibald wrote:
> On 08/11/06, Pierre GM <pgmdevlist at gmail.com> wrote:
>
>   
>> I like your idea, but not its implementation. If MA.masked_singleton is
>> defined as an object, as you suggest, then the dtype of the ndarray it is
>> passed to becomes 'object', as you pointed out, and that is not something one
>> would naturally expec, as basic numerical functions don't  work well  with the
>> 'object' dtype (just try  N.sqrt(N.array([1],dtype=N.object)) to see what I
>> mean).
>> Even if we can construct a mask rather easily at the creation of the masked
>> array, following your 'a==masked' suggestion, we still need to get the dtype
>> of the non-masked section, and that doesn't seem trivial...
>>     
>
> A good candidate for "should be masked" marked is NaN. It is supposed
> to mean, more or less, "no sensible value". Unfortunately, integer
> types do not have such a special value. It's also conceivable that
> some user might want to keep NaNs in their array separate from the
> mask. Finally, on some hardware, operations with NaN are very slow (so
> leaving them in the array, even masked, might not be a good idea).
>   
It has always been my experience (on various flavors or Pentium) that 
operating on NANs is extremely slow. Does anyone know on what hardware 
NANs are *not* slow? Of course it's always possible I just never notice 
NANs on hardware where they aren't slow.


[SNIP]

-tim


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