RE: st: repeated values of a variable

[Richard Williams <Richard.A.Williams.5@nd.edu>]

At 10:17 AM 3/17/2004 +0000, Nick Cox wrote:
> Note that
>
> . bysort id : drop if _N == 1
>
> is (nearly) equivalent. It's more direct;
> but note the side-effect of -sort-ing.
That is good.  In general, data sets should have id numbers; sort commands 
can be a little scary without them, and ado files may sort your data 
without your knowledge.  It would be sort of a shame if you had thousands 
of survey questionnaires coded and then couldn't link the data back to 
their original sources.

If missing data on id is a concern, modify the above to

bysort id : drop if _N == 1 | missing(id)


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Richard Williams, Notre Dame Dept of Sociology
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