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st: number of unique values within an observation


From   "Scott Imberman" <Imberman@econ.bsos.umd.edu>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: number of unique values within an observation
Date   Fri, 30 Sep 2005 14:56:55 -0400

Dear Statalist,

I was wondering if there is s a simple way to count the number of
unique values in a variable list for each observation.  For example, i
am looking at the id numbers for colleges that a set of student attends.
 A student may list having attended a college in multiple years like
this:

year     id

1995     3
1996     2
1997     3
1998     3

I want to know how many unique schools the student attended (in this
example the answer is 2).  Thanks for your help.

Sincerely,

Scott Imberman

-------------------------------------------------------------------
Scott Andrew Imberman

Department of Economics
3105 Tydings Hall, University of Maryland
College Park, MD 20742
Voice: (301) 405-4534
Fax: (301) 405-3542

imberman@econ.umd.edu

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