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Re: st: Why can't I egen means with pweights?


From   n j cox <n.j.cox@durham.ac.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Why can't I egen means with pweights?
Date   Wed, 23 Apr 2003 18:19:06 +0100

Laura Schechter wrote:

   I have been trying to program a specific bootstrap in stata, and need
to use the weighted means of certain variables over time. Unfortunately,
it seems to me that the egen command doesn't work with weights. For now, I
have just been using the series of commands
   svymean varname [pweight=x], by(month)
   matrix e=e(est)
   generate ET=el(e,1,1) if month==1
   replace ET=el(e,1,2) if month==2
      etc. etc. etc.
But this is really slow, and it would be so convenient if the egen command
would work with weights so I could just say something like
    egen ET=mean(varname) [pweight=x], by(month)
Does anyone know a way of doing this??
The answer to your title question is: because weights
were never part of the syntax of -egen-. I don't know why.

An answer to your end question is to program it
directly. A similar problem is documented at
"I want to calculate a variable containing weighted group summary statistics, but I do not want to collapse the data and egen does not support weights. How can I do this?"
http://www.stata.com/support/faqs/data/weighted.html

In your case -levels- is presumably unnecessary if -month-
takes on values 1(1)12.

Hence

gen ET = .
qui forval i = 1/12 {
su varname [pweight=x] if month == `i', meanonly
replace ET = r(mean) if month == `i'
}

Nick
n.j.cox@durham.ac.uk

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