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


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st:How to do analysis if the same variable exists in one dataset and is missing or contains no observation in another database?
Date   Fri, 8 Aug 2003 11:25:51 +0100

adiallo5@worldbank.org
>
> Thanks Nick and David for the help.
>
> David, I mean the exact correspondence: var1 for a, var2 for b, etc.
>
> If a variable is absent, it would be preferable not to
> create it, since the
> program is huge.
> For example, if a does not exist or contains no
> observation, thus, it would be
> preferable not to create var1.
> Even though we create new variables with missing values,
> they would be
> irrelevant for my regressions.
>
> For var5, if at least one of the variables exists, then I
> want to use it to
> create var5. If not, it will not be created.
>
> Nick, all the code is there. My intend is simple.
> Let me rewrite all my program below: my dependent variable
> is depvar (which is
> common to all files).
>
> local varlist1 "a b c d e f g h"
> foreach x of local varlist1 {
> capture confirm var `x'
> if _rc==0 {
>           capture assert mi(`x')
>           if _rc==0 {
>                     drop `x'
>          }
> else {
>          g var1=a
>          g var2=b
>          g var3=c
>          g var4=d
>          g var5=.
>          replace var5=1 if e==1| f==1| g==1| h==1
>         }
>    }
> regress depvar var1 var2 var3 var4 var5     /*if one of
> them exists*/
>
> The first suggestion of Nick seems good, but since I have a
> lot of variables to
> create, it will be very difficult to rewrite the code for
> each of them.
> I will try his second suggestion.

You are correct. My first comment does not
apply, as I misread your code. But perhaps you now have
the ingredients of a solution from various suggestions.

Nick
n.j.cox@durham.ac.uk

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