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st: Re: Re: Re: how to keep maximum value


From   "Michael Blasnik" <michael.blasnik@verizon.net>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: Re: Re: how to keep maximum value
Date   Mon, 25 Sep 2006 07:26:59 -0400

The collapse approach is different in a couple of ways.  First, if there are 
other variables in the dataset, then the collapse approach will omit them 
while the by approach will include them.  Second, the by approach will 
select missing values on var1 as the max, so if there are missing values 
they should probably be dropped before executing the command (assuming you 
don't want missing to mean max).  Third, the by approach wil be faster, 
although the speed difference would probably only be noticeable in very 
large datasets.

Michael Blasnik

----- Original Message ----- 
From: "Rodrigo A. Alfaro" <ralfaro76@hotmail.com>
To: <statalist@hsphsun2.harvard.edu>
Sent: Sunday, September 24, 2006 10:42 PM
Subject: st: Re: Re: how to keep maximum value


> An alternative
>
> collapse (max) var1, by(year)
>
> ----- Original Message ----- 
> From: "Michael Blasnik" <michael.blasnik@verizon.net>
> To: <statalist@hsphsun2.harvard.edu>
> Sent: Sunday, September 24, 2006 10:01 PM
> Subject: st: Re: how to keep maximum value
>
>
>
> bysort year (var1): keep if _n==_N

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