Re: st: Map logical operator across varlist?

[David Kantor <kantor.d@att.net>]

I don't think you can "map" an arbitrary operator.

But there are many ways to program your problem.

If you create a set of indicators as to whether the med variables are 
nonmissing (and by the way, a more generally correct test is ~mi() )...
 gen byte nonmis_med1 = ~mi(med1)
 gen byte nonmis_med2 = ~mi(med2)
  etc., (and that can be made into a loop)

then if you have the trinary module, you can do

egen byte med_ok = rtvor(nonmis_*)

this will give you the row-or of the arguments.  (The fact that it is 
3-valued logic is irrelevant.)
Then you can
list med* if med_ok


To get trinary,
ssc inst trinary

I hope this helps.
--David


At 03:01 PM 1/17/2007, Joel J. Adamson wrote:

> Does anyone know how to map a logical operation (e.g., | or &) across
> a list so that I can save myself some typing?
>
> Let me give you an example (the one that prompted the search for an
> answer):
>
> I want to list a set of variables, only if an observation  is not missing
> for the variables in question.  We usually handle this by constructing
> a small logical expression:
>
> l med1 med2 if (med1~=.|med2~=.)
>
> However, if I have six, or a hundred "med" variables (med*), it would
> be easier (less error-prone) to type:
>
> l med* if |(med*~=.)
>
> Where the "|" before the "(" maps the operation onto the expanded list
> of variables.
>
> I know that Scheme (and hence probably S) have a function called "map"
> that maps any operation onto a list, e.g.,
>
> (map or '(1 2 3 ... ))
>
> Does anyone know of a similar construct in Stata?  How about an egen
> function that would accomplish the same goal?
>
> Thanks,
> Joel
> --
> Joel J. Adamson
> Biostatistician
> Pediatric Psychopharmacology Research Unit
> Massachusetts General Hospital
> Boston, MA  02114
> (617) 643-1432
> (303) 880-3109
> [...]
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