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RE: st: RE: creating expanded records with indicator variables, where different ID's reside in the same rows


From   "Nick Cox" <[email protected]>
To   <[email protected]>
Subject   RE: st: RE: creating expanded records with indicator variables, where different ID's reside in the same rows
Date   Wed, 21 Oct 2009 18:52:40 +0100

OK. Try this: 

input a b 
5 5 
6 11
end
gen long id = _n 
expand 2 if a != b 
bysort id : replace id = cond(_n == 1, a, b) 
replace a = a == id 
replace b = b == id 
l


Nick 
[email protected] 


-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Michael
McCulloch
Sent: 21 October 2009 18:21
To: [email protected]
Subject: Re: st: RE: creating expanded records with indicator variables,
where different ID's reside in the same rows

Sorry Nick, yes you're correct, it should be:
id	A	B
5	1	1
6	1	0
11	0	1
Michael

On Oct 21, 2009, at 10:18 AM, Nick Cox wrote:

> Sorry, but I can't even follow your first two steps. Why isn't the
> second observation 6 1 0?
>
> Nick
> [email protected]
>
> Michael McCulloch
>
> I have a data structure that has been gathered as follows, where each
> cell contains the subject ID if A is true, and similarly for B.
> Therefore, for subject 5, I have A=yes and B=yes, whereas for subjects
> 6 and 11, only B=yes.
>
> A	B
> 5	5
> 6	11
>
> I'd like to transform the data structure such that each row would have
> ID, and indicator variables for A and B.
> id	A	B
> 5	1	1
> 6	0	1
> 11	0	1
>
> I've tried an approach like this, where I create indicator variables
> but A and B, but am not sure how to "expand" from  the data structure
> where different ID's reside in the same rows.
> 	. gen id1=a
> 	. gen id2=b
> 	. gen aa=1 if a!=.
> 	. gen bb=1 if b!=.
>
> It also looks like -reshape- is not suitable because different ID's
> reside in the same rows.
> Any advice would be appreciated.

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