[R] Why can't R understand if(num!=NA)?

[David Winsemius]

On May 3, 2013, at 10:58 PM, peter dalgaard wrote:

> 
> On May 3, 2013, at 21:36 , David Winsemius wrote:
> 
>> 
>> On May 3, 2013, at 10:46 AM, peter dalgaard wrote:
>>> 
>>> 
>>> Because comparison with an unknown value yields an unknown result. 
>> 
>> Anything else would violate the Second Law of Thermodynamics. We cannot have comparisons reducing entropy, now can we? Uncertainty cannot run uphill.
> 
> Now what does this say about SAS, where the missing value is smaller than all regular numbers? I.e.,
> 
> DATA;
>  iteen = (age < 20);
> 
> turns people of unknown age into instant teenagers.

And are handled as zero when included in calculations using SUM ( as, I also read, does SPSS). 

So SAS comparisons are still increasing entropy. Quantum mechanics says there is no real vacuum state, so maybe that's where those not-really-missing missing values are ending up after they confound our notions of existence.

-- 
David Winsemius
Alameda, CA, USA