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Re: st: Speaking Stata: by varlist


From   "Joel E. Pike" <jpike@bus.wisc.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Speaking Stata: by varlist
Date   Sat, 22 Jun 2002 16:13:53 -0500

At 03:36 PM 6/22/02 -0500, you wrote:
At 11:49 AM 6/22/2002 -0400, you wrote:
Dear Statalisters,

In Stata, the

bysort varlist: list varlist if _N>1

is supposed to find duplicates with respect to the bysort varlist.

I have a data set, and I know by the ID variable there is no duplicates, because if I use

bys ID: gen count=_N
tab count

I get count all equal to 1.

However, if I use

bys ID: list varlist if N>1

Stata starts to list every observation from the top.

Why is this happening?
One explanation is that your code:
bys ID: list varlist if N>1

should be

bys ID: list varlist if _N>1

Fred
This actually doesn't make any difference. Either syntax gives you the same result, as I confirmed with my own data after I noticed the same thing. I think in the syntax above, _N is not found, so that for every observation _N>1.

Joel





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Fred Wolfe Tel (316) 263-2125
National Data Bank for Rheumatic Diseases Fax (316) 263-0761
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