Mark Wiebe writes:
> On Wed, Jul 6, 2011 at 12:41 PM, Pierre GM <[email protected]> wrote:
> Ah, semantics...
> On Jul 6, 2011, at 5:40 PM, Mark Wiebe wrote:
>>
>> NA (Not Available)
>> A placeholder for a value which is unknown to computations. That
>> value may be temporarily hidden with a mask, may have been lost
>> due to hard drive corruption, or gone for any number of reasons.
>> This is the same as NA in the R project.
> I have a problem with 'temporarily hidden with a mask'. In my mind, the
> concept of NA carries a notion of perennation. The data is just not
> available, just as a NaN is just not a number.
> Yes, this gets directly to what I've been meaning when I say NA vs IGNORE is
> independent of mask vs bitpattern. The way I'm trying to structure things, NA
> vs IGNORE only affects the semantic meaning, i.e. the outputs produced by
> computations. This is precisely why I put 'temporarily hidden with a mask'
> first, to make that more clear.
>
>> IGNORE (Skip/Ignore)
>> A placeholder which should be treated by computations as if no value
> does
>> or could exist there. For sums, this means act as if the value
>> were zero, and for products, this means act as if the value were one.
>> It's as if the array were compressed in some fashion to not include
>> that element.
> A data temporarily hidden by a mask becomes np.IGNORE.
> Are you willing to suspend the idea of that implication for the purposes of
> the
> present discussion? If not, do you see a way to amend things so that masked
> NAs
> and bitpattern-based IGNOREs make sense? Would renaming IGNORE to SKIP be more
> clear, perhaps?
Yes, I was going to propose something similar. The NA/IGNORE is about
the propagation mechanism, and this is not as explicit in NA as it is in
IGNORE. So maybe, and avoiding too much concept renaming:
NA (Propagate)
...
IGNORE (Skip)
...
Lluis
--
"And it's much the same thing with knowledge, for whenever you learn
something new, the whole world becomes that much richer."
-- The Princess of Pure Reason, as told by Norton Juster in The Phantom
Tollbooth
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