st: RE: RE: Unexpected error from -merge-

["Radwin, David" <dradwin@rti.org>]

Yes, and please consider using -isid-, which detects missing values as well as duplicate values. Occasionally this may save you from trouble. For example:

. clear

. set obs 100
obs was 0, now 100

. gen cbhiind=_n in 1/99
(1 missing value generated)

. duplicates report cbhiind

Duplicates in terms of cbhiind

--------------------------------------
   copies | observations       surplus
----------+---------------------------
        1 |          100             0
--------------------------------------

. isid cbhiind
variable cbhiind should never be missing
r(459);

David
--
David Radwin
Senior Research Associate
Education Studies Division
RTI International
2150 Shattuck Ave., Suite 800
Berkeley, CA 94704
Phone: 510-665-8274

www.rti.org

> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-
> statalist@hsphsun2.harvard.edu] On Behalf Of Joe Canner
> Sent: Monday, September 23, 2013 8:48 AM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: RE: Unexpected error from -merge-
> 
> By default when you do -duplicates report-, it is looking for duplicates
> with respect to every variable in your data set, which is why you have all
> unique records.  What you want is -duplicates report actpsid- which will
> give you just the duplicates with respect to the variable you are trying
> to merge on.
> 
> Regards,
> Joe Canner
> Johns Hopkins University School of Medicine
> 
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-
> statalist@hsphsun2.harvard.edu] On Behalf Of Jacob-Jan Koopmans
> Sent: Monday, September 23, 2013 11:21 AM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: Unexpected error from -merge-
> 
> Dear list members,
> 
> I am receiving an unexpected error when merging data.
> I am using stata 12.
> 
> I am trying to merge data in the following way:
> "sort actpsid
> merge 1:m actpsid using "cbhiind" ".
> 
> This, however, results in the following error:
> "variable actpsid(my individual identifier) does not uniquely identify
> observations in the master data r(459)."
> This would normally suggest(as far as I know), there are duplicates of
> actpsid in the master data. However, when checking for duplicates by
> using: duplicates report. I receive the following nice report:
> 
> "Duplicates in terms of all variables
> --------------------------------------------------------
>    copies | observations       surplus
> ----------+--------------------------------------------
>         1 |         8772             0
> --------------------------------------------------------"
> 
> Therefore, I suppose the error is not resulting from duplicates in my
> identifier variable.
> 
> I would thus like to ask whether there are other reasons why the above
> mentioned error appears.
> 
> Kind regards,
> Jacob-Jan Koopmans

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