RE: st: Re: Making sure identifiers are unique

["louis boakye-yiadom" <louisby@hotmail.com>]

Michael,
Thanks a lot. I'll do that.

Louis


> I guess you need to look at the help for collapse some more.   -collapse- 
> calculates whatever summary statistics you specify for each unique 
> combination of the by variable list and then collapses the dataset to one 
> observation for each of these unique combinations.  It will, by design, 
> always result in the by varlist becoming a unique identifier.
>
> Michael Blasnik
> michael.blasnik@verizon.net
>
>
> ----- Original Message ----- From: "louis boakye-yiadom" 
> <louisby@hotmail.com>
> To: <statalist@hsphsun2.harvard.edu>
> Sent: Tuesday, March 08, 2005 10:48 AM
> Subject: st: Making sure identifiers are unique
>
>
>
> > Dear all,
> > I've been trying to determine the identifiers of a data set, and to ensure 
> > they're unique. Suspecting the variables, "region" and "district" are the 
> > identifiers, I gave the commands below, and got the output shown:
> > . sort region district
> > . by region district: assert _N==1
> > 62 contradictions in 97 by-groups
> > assertion is false
> > r(9);
> >
> > Owing to the fact that I'm more interested in the "district"-level data, I 
> > wanted to know whether a collapsed version of the data will have unique 
> > identifiers. I therefore gave the following set of commands and got the 
> > results shown:
> > . gen x=1
> > . collapse (count) x, by (region district)
> > . sort region district
> > . by region district: assert _N==1
> >
> > My question is: What can account for the collaped data being uniquely 
> > identified by "region" and "district", whilst the original data are not? 
> > I'm using version 8.2.
> >
> > Many thanks,
> > Louis

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