Re: st: Using -egen- with existing variable

[David Kantor <dkantor@jhu.edu>]

At 06:18 PM 6/2/2005 -0600, Mike Lacey wrote:
> I want to use -egen- to create a total out of a1, a2, a3 in one situation, 
> b1, b2, b3 in another situation, etc., but am running
> into problems about how to use egen on an existing variable.
>
> For example:
>
> *I would like to do something like:
> egen tot = rowtotal(a1 a3 a3) if situation = 1
> egen tot =  rowtotal(b1 b2 b3) if situation = 2
> ... etc.
> egen tot = rowtotal(z1 z3 z3)   if situation = 10
> *
> This of course is syntactically invalid.  So, the kludge I
> came up with was:
>
> egen tot1 = rowtotal(a1 a3 a3) if situation = 1
> egen tot2 =  rowtotal(b1 b2 b3) if situation = 2
> ...etc.
> egen tot10 = rowtotal(z1 z3 z3)   if situation = 10
> generate total = rowtotal(tot1-tot10)
> * Make total missing where appropriate
> egen nmiss = rowmiss(tot1-tot10)
> replace total = . if nmiss == 10
> drop nmiss tot1=tot10
>
> What would be a Stata-ish way to do this?
>
> Thanks,
>
> Mike Lacy
> Fort Collins CO USA
> (970) 491-6721 office
What you did is fine, putting aside minor grammatical and typographic 
missteps.  I also don't know about rowtotal. You may have intended rsum 
instead -- unless there is a rowtotal egen function in Stata 9, which I 
don't have yet.

Here's another way to do it, just a bit different from yours:

egen tot1 = rsum(a1 a2 a3)
egen tot2 = rsum(b1 b2 b3)
 ...
egen tot10 = rsum(z1 z2 z3)

#delimit ;
gen total =
cond(situation==1, tot1,
cond(situation==2, tot2,
 ...
cond(situation==10, tot10,
. ))))))))));

----
I hope this helps.
-- David

David Kantor
Institute for Policy Studies
Johns Hopkins University
dkantor@jhu.edu
410-516-5404

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