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RE: st: Again-Unique Case ID in Large Panel


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Again-Unique Case ID in Large Panel
Date   Thu, 5 Aug 2004 10:37:24 +0100

Is the message 

"id*Delta(time) does not uniquely identify observations."

going to solve this problem? As I understand it, 
the question of uniqueness is absolute and not 
dependent on what is displayed given some -width()-. 

As StataCorp will be touching the code for -xtdes-, 
I suggest that they also touch the on-line help and point 
to the official commands -isid- and -duplicates- 
as tools which it seems can be helpful here. The 
manual entry can follow in due course. 

Nick 
n.j.cox@durham.ac.uk 

Richard Gates
 
> The previous version of -xtdes- could exceed the maximum 
> number of variables
> when attempting to identify the participation patterns if the 
> time range was
> large relative to the minimum time increment.
>                                                               
>                   
> The new code will detect that the participation patterns 
> display will exceed
> the maximum display width, -width-. The current default width 
> is 100 which on
> most displays will wrap and be illegible anyway. The logic in 
> -xtdes- will find
> the time increment that will give the display a width close 
> to -width-. I
> enroneously used the logic that traps this condition to also 
> identify that time by
> id does not uniquely identify an observation.
>                                                               
>                   
> As Nick pointed out, it is simply a bogus message (in Steve's 
> case) and more
> logic needs to be added to detect whether or not time by id 
> uniquely identifies
> an observation in this situation. Or maybe it should say, 
> "id*Delta(time)
> does not uniquely identify observations."

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