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

From   "Nick Cox" <[email protected]>
To   <[email protected]>
Subject   st: RE: RE: "unique" with "by"
Date   Wed, 19 Apr 2006 17:28:53 +0100

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

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?

[email protected] 

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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