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Re: st: Workflow to combine dummy variables?


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Workflow to combine dummy variables?
Date   Wed, 21 Nov 2007 07:10:04 +0000 (GMT)

--- John A Stefanic <stefanic@Colorado.EDU> wrote:
> I'm having a lot of trouble combining dummy variables and creating a
> new variable where I count dummy variables.
> 
> So, I have a dataset (GSS) with variables SPOUSE1, CHILD1, SPOUSE2,  
> CHILD2, SPOUSE3, CHILD3, indicating if person 1, 2, and 3 are a
> spouse or child.  In each variable, 1 == Mentioned, 2 == Not
> Mentioned.
> 
> Since both SPOUSE1 and CHILD1 are kin, I want to recode them into a  
> new variable, KIN1, if either SPOUSE1 or CHILD1 == 1.  So I tried:
> 
> recode SPOUSE1 SPOUSE2 CHILD1 CHILD2 (2 = 0) (1 = 1) (.a = .a) (.c  
> = .c), pre(RE)
> 
> Then, I did this:
> 
> generate int KIN1 = RESPOUSE1 + RECHILD1
> 
> This works fine, I get a new variable KIN1, with values 1 (person is 
> 
> kin) or 0 (person not kin).  But, now I want to make another new  
> variable, NUMKIN, indicating the sum of variables KIN1, KIN2, and
> KIN3.
> 
> So, I did this:
> 
> generate int NUMKIN == KIN1 + KIN2 + KIN3
> 
> But, my results exclude a number of cases as missing data.  If the  
> case is not a "1" for KIN3, it is excluded!  Is there something I can
>  
> do to change my workflow to make this process easier?  How does one  
> combine dummy variables in STATA?

You can do that with -egen- and the -rowtotal- expression:

egen int numkin = rowtotal(RESP* RECHI*)

As a matter of personal taste I don't like variables names in capital
letters (too much typing), so one of the first things I do when getting
GSS data is to turn all variable names into lower case:

foreach var of varlist _all {
	local lvar = lower("`var'")
	rename `var' `lvar'
}

Hope this helps,
Maaren

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


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