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
>
>[email protected]
>
>*
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Econalytics
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