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Re: st: RE: RE: "unique" with "by"


From   "Shige Song" <shigesong@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: RE: "unique" with "by"
Date   Fri, 21 Apr 2006 12:46:25 +0800

Thanks to both Nick and David, both solutions work well.

Best,
Shige

On 4/20/06, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> Shige Song is using a user-written program -unique-,
> installable from SSC.
>
> Please recall the request in the FAQ to
> explain non-official commands you are using.
>
> I am always fond of answers like David Harrison's that explain
> how -levelsof- can solve your problem, as -levelsof- is
> a command I like. But there are other alternatives. One is
> to use -distinct-, also from SSC, which does support
> -by:-.
>
> bysort hhid: distinct id
>
> gets you there in one.
>
> Whether the problem is one of distinct or of unique
> observations is discussed in a unique FAQ, which
> also explains how to tackle it from first principles:
>
> FAQ     . . . . . . . . . . . . . . . . . . .  Number of distinct observations
>         4/02    How do I compute the number of distinct observations?
>                 http://www.stata.com/support/faqs/data/distinct.html
>
> Nick
> n.j.cox@durham.ac.uk
>
> David Harrison
>
> > levelsof hhid, local(lev)
> > foreach h of local lev {
> >     unique id if hhid==`h' /* make this "`h'" if hhid is string */
> > }
>
> Shige Song
>
> > I want to get count of unique values of a variable and I want
> > to use it
> > conjuction with "by" like this:
> >
> > sort hhid
> > by hhid: unique id
> >
> > But unfortunately the UNIQUE command does not allow the use of "by".
> > Are there other options? Thanks!
>
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