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Re: st: How to randomly pick one observation from all?


From   Ulrich Kohler <ukohler@sowi.uni-mannheim.de>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: How to randomly pick one observation from all?
Date   Wed, 12 Jun 2002 09:00:50 +0000

Yanjun Bao  wrote
> We have say, by one id, four observations under a variable.  We want STATA
> to randomly pick one observation each time it is asked.  We want to use the
> randomly picked observation for each id in regression.


You can sort by a random variable within each person and than pick the first 
observation or each person. If "id" is the identifier for observation the 
following should do it:

.. set seed 731           /*  Change seed to whatever you want */
.. gen r = uniform()      
.. by id (r), sort: gen select = _n==1
.. regress yvar xvars if select


hope this helps
uli

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