Re: st:How to do analysis if the same variable exists in one datasetand is missing or contains no observation in another database?

[David Kantor <dkantor@jhu.edu>]

To Adiallo5:

-confirm existence-

will just confirm that there is anything at all following it, so
 confirm existence (`x')
will always be true.

You probably intended...
 capture confirm var `x'

But then, it is inside a -foreach- that loops through a varlist, so `x' 
will always be a variable (assuming that v* does expand to at least one 
variable).  So that doesn't do any good either.

Perhaps you have a specific list of variables in mind, whose elements may 
or may not be present an any given dataset.  Suppose this is in a local 
called vlist1.  You would assign its value in a -local- command.  Note that 
it is not a varlist in the true sense, as some elements possibly don't 
exist as variables for the current dataset.

Then you would do..

foreach x of local vlist1 {
capture confirm var `x'
  if _rc==0 {
    ... do whatever you want with `x' ...
  }
  else {
    display "`x' does not exist"
}

(Note that is -if _rc==0-, rather than -if _rc!=0-.)

If you want to separate out the variables that are completely missing, you 
would want to do...

foreach x of local vlist1 {
capture confirm var `x'
  if _rc==0 {
    capture assert mi(`x')
      if _rc==0 {
        disp "`x' is all missing"
      }
      else {
       ... do whatever you want with `x' ...
      }
  }
  else {
    display "`x' does not exist"
}

I hope this is what you were looking for.
-- David

At 06:08 PM 8/5/2003 -0400, you wrote:

> Dear stata users,
>
> I have the same survey conducted in several developing countries.
> The databases contain almost the same variables (most of the time
> coded the same way, but differently sometimes).
>
> In each database, I want to tell stata to check for a variable, and if it does
> exist or does
> contain observations, to perform some task.
>
> I coded for example:
>
> foreach x of varlist v* {
>       capture confirm existence (`x')
>       if _rc!=0 {
>                       sum `x'
>                       recode `x' 1=1 2/3=2 4/*=3
>      }
>     else {
>                   display "`x' does not exist or may contain no observation"
> }
>
> But this does not seem to work. I am using stata 8.
>
> How to do if the codification for the same variable is different across
> databases?
>
> Many thanks.
David Kantor
Institute for Policy Studies

Johns Hopkins University
dkantor@jhu.edu
410-516-5404

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