st: RE: Unexpected error from -merge-

[Joe Canner <jcanner1@jhmi.edu>]

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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