st: Re: merging on same using dataset

["Michael Blasnik" <michael.blasnik@verizon.net>]

The key here I think is to use the -fillin- command to expand the master 
dataset and the use a single merge.  You can flag the unchosen choices using 
the _fillin var.  I showed how to change the _merge var based on this.

use master
fillin Indiv choice
sort choice
merge choice using usingdata
replace _merge=2 if _fillin==1

Michael Blasnik

----- Original Message ----- 
From: "Munro, Cameron" <munro@rand.org>
To: <statalist@hsphsun2.harvard.edu>
Sent: Friday, February 03, 2006 11:31 AM
Subject: st: merging on same using dataset



> I'm building up a choice dataset where I need to read in the 
> characteristics of the alternatives for each individual. A simplified 
> example of what I want to happen:
> Master data -
> Indiv    Choice
> 1        2
> 2        4
> ...      ...
>
> Using data -
> Choice  x1   x2 ...
> 1       10   12
> 2       14   13
> 3       17   18
> 4       43   13
> 5       12   15
>
> Desired output -
> Indiv  Choice  x1  x2  _merge
> 1      1       10  12     2
> 1      2       14  13     3
> 1      3       17  18     2
> 1      4       43  13     2
> 1      5       12  15     2
> 2      1       10  12     2
> 2      2       14  13     2
> 2      3       17  18     2
> 2      4       43  13     3
> 2      5       12  15     2
>
> In effect, what I want to do is merge sequentially down each observation 
> in the master dataset in turn. The only way I can achieve this at the 
> moment is to create separate files for each obs and then append them 
> together after running the merge on each separately. But this results in 
> many files, and is slow. Is there a better way?
>
> Cheers
>
> Cameron.
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