In addition to Nick's suggestion of using -reshape-, another possibility is
to use -levelsof- and the macro extended functions (assuming your cross
sections are not too large):
. l, noobs
+------------------------------------+
| gvkey psic ssic year subno |
|------------------------------------|
| 1223 4767 4743 1999 1 |
| 1223 4767 4763 1999 2 |
| 1223 4757 4767 1999 3 |
| 1223 4767 4753 1999 4 |
| 1223 4777 4787 1999 5 |
|------------------------------------|
| 1223 4767 4743 1999 6 |
+------------------------------------+
. levelsof psic, local(p)
4757 4767 4777
. levelsof ssic, local(s)
4743 4753 4763 4767 4787
. local total: list s | p
. local total:list uniq total
. local count:list sizeof total
. gen nvals = `count'
. l, noobs
+--------------------------------------------+
| gvkey psic ssic year subno nvals |
|--------------------------------------------|
| 1223 4767 4743 1999 1 7 |
| 1223 4767 4763 1999 2 7 |
| 1223 4757 4767 1999 3 7 |
| 1223 4767 4753 1999 4 7 |
| 1223 4777 4787 1999 5 7 |
|--------------------------------------------|
| 1223 4767 4743 1999 6 7 |
+--------------------------------------------+
Scott
> -----Original Message-----
> From: [email protected] [mailto:owner-
> [email protected]] On Behalf Of Wanli Zhao
> Sent: Saturday, June 18, 2005 3:17 PM
> To: [email protected]
> Subject: st: RE: unique value count in several variables
>
> Thanks, Nick. I looked into the suggestions and I think I might have
> confused you on my problem. My panel data is like this:
> Gvkey psic ssic year subno
> 1223 4767 4743 1999 1
> 1223 4767 4763 1999 2
> 1223 4757 4767 1999 3
> 1223 4767 4753 1999 4
> 1223 4777 4787 1999 5
> 1223 4767 4743 1999 6
>
> Using command unique, I can count the distinct values of psic and ssic by
> gvkey by year. So for psic it's 3 and for ssic it's 5. what I want is to
> count the distinct values of both psic and ssic by gvkey by year. In this
> case, it's 7 (4767, 4757, 4777, 4743, 4763, 4753, 4787). How to generate a
> new variable for my purpose? Hope I'm clear now. Pls help.
>
> Thanks.
> Wanli Zhao
>
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