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

[peter dalgaard]

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.

-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com