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st: Again-Unique Case ID in Large Panel

From   "Stephen V. Burks" <>
Subject   st: Again-Unique Case ID in Large Panel
Date   Wed, 04 Aug 2004 12:18:05 -0500

Hi, Folks.

Now I wonder if I am reporting a bug. As per Nick's suggestion
(thanks, Nick) I looked up -duplicates- and ran it.

(1) using -duplicates report-

. duplicates report DRVNUM CDATE

Duplicates in terms of DRVNUM CDATE
copies | observations surplus
1 | 1322511 0

(2) using -duplicates list-

. duplicates list DRVNUM CDATE
Duplicates in terms of DRVNUM CDATE
(0 observations are duplicates)

If I read this correctly, one version of -duplicates- says I have
a single duplicate (the last case in the file), while the other
says I have none. Also, -xtdes- still says that DRVNUM and
CDATE do not uniquely identify cases.

I looked in the data browser, and the last case is NOT a duplicate.
While DRVNUM is the same as the case before, CDATE is not.

If my interpretation of the output is correct then my best guess is
that -xtdes- is wrong to say I do not have unique identification,
and whatever bug causes this might also be behind the apparently
incorrect response from -duplicates report-. In any event, it seems
to be a problem that -duplicates list- and -xtdes- do not agree.

Any better ideas?


P.S. My version of Stata is 8.2 for WinXP, with current updates.

*Stephen V. Burks, Ph.D.
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*University of Minnesota, Morris
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