Re: [Gretl-devel] bug with missings, dummies (and panel?)
Sorry for joining late. I think gretl handles missing values rather
well. I am saying this because I have applied the so called Wilkinson
Tests to gretl, which assesses the handling of missing values among
other basic statistical functionality. (The test results are available
here: http://ideas.repec.org/h/ehu/ehucha/01-16.html )
Suppose we have a series called MISS consisting of missing values
series NEW =MISS+1
returns all missing values because we cannot know what happens if 1 is
added to a missing (unknown) number.
series NEW=MISS*0
on the other hand returns zeroes because we know (as Allin mentioned)
the result here.
Similarly
series NEW=MISS/0
returns missing values.
This behavior is, of course, valid when all values are numerical and
finite, which is IMO OK considering our standard methods such as using
dummies etc. Finally, I have to mention that Eviews retuns
MISS*0=MISS.
Cheers
Talha
On Wed, Apr 14, 2010 at 3:26 AM, Allin Cottrell <cottrell(a)wfu.edu> wrote:
On Tue, 13 Apr 2010, Riccardo (Jack) Lucchetti wrote:
> On Tue, 13 Apr 2010, Berend Hasselman wrote:
> > I feel that The R and Octave result of NA for 0*NA is perfect reasonable
> > (in a numeric context). I prefer it.
>
> Matter of taste.
Actually, I think it's a bit more than a matter of taste. If a
program evaluates 0*NA as NA I submit that shows that the program
does not implement the concept of "NA" as missing value.
The original source of "true" NAs in econometrics is observations
that were not made, were lost, or are otherwise unavailable. In
that context, as Jack said, "NA" is a place-holder for an unknown
value, but if it's the unknown value of a measurable quantity it
cannot be infinity or "Not a Number" (which is a place-holder for
a mathematical error), and multiplication by zero yields zero for
any such unknown but in principle valid value.
If a program has 0*NA = NA it is treating NAs as if they were
nans, which in general is not correct (though is is convenient for
the coder not to have to make the distinction).
Allin
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