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Re: st: number of unique values within an observation


From   "Eric G. Wruck" <ewruck@econalytics.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: number of unique values within an observation
Date   Fri, 30 Sep 2005 16:36:13 -0400

Hi Scott:

Here is a way to do it:

. egen unique = tag(id)

. egen no_unique = total(unique)

. l

     +-------------------------------+
     | year   id   unique   no_uni~e |
     |-------------------------------|
  1. | 1995    3        1          2 |
  2. | 1996    2        1          2 |
  3. | 1997    3        0          2 |
  4. | 1998    3        0          2 |
     +-------------------------------+

.

Of course, you may want to do this by(student).

Eric



>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
>
>*
>*   For searches and help try:
>*   http://www.stata.com/support/faqs/res/findit.html
>*   http://www.stata.com/support/statalist/faq
>*   http://www.ats.ucla.edu/stat/stata/


-- 

===================================================

       Eric G. Wruck
       Econalytics
       2535 Sherwood Road
       Columbus, OH  43209

       ph:      614.231.5034
       cell:    614.330.8846
       eFax:    614.573.6639
       eMail:   ewruck@econalytics.com
       website: http://www.econalytics.com

====================================================
*
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