the confirm and capture combination works much better than my original
approach. Thanks, Tim
On 1/29/08, Maarten buis <[email protected]> wrote:
> -- Nick wrote:
> > If the argument is not a variable in the dataset, the return code
> > from -confirm- will be positive, and if it is, the return code will
> be
> > zero. So,
> >
> > !_rc
> >
> > is non-zero if it's present and zero otherwise. So Maarten's second
> > example does not read quite correctly.
>
> The code is a bit cryptic, but it is correct. In my code !_rc should
> return false if the the variable is absent. The ! negates the statement
> following it: _rc. In Stata 0 is false and any positive number is true,
> so if the variable is absent _rc will contain a positive number (true)
> and ! negates it and turns it into false (0). If the variable is
> present than _rc contains false (0) and ! negates it and turns it into
> true. The way you can make sense of this code is to read -if !_rc- as
> "if no problem".
>
> *----------- begin example ------------
> sysuse auto, clear
> capture confirm variable price
> if !_rc {
> di "price is pressent"
> }
> sysuse nlsw88, clear
> capture confirm variable price
> if !_rc {
> di "price is present"
> }
> *------------ end example -------------
> (For more on how to use examples I sent to the Statalist, see
> http://home.fsw.vu.nl/m.buis/stata/exampleFAQ.html )
>
> Hope this helps,
> Maarten
>
> -----------------------------------------
> Maarten L. Buis
> Department of Social Research Methodology
> Vrije Universiteit Amsterdam
> Boelelaan 1081
> 1081 HV Amsterdam
> The Netherlands
>
> visiting address:
> Buitenveldertselaan 3 (Metropolitan), room Z434
>
> +31 20 5986715
>
> http://home.fsw.vu.nl/m.buis/
> -----------------------------------------
>
>
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