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Re: st: How to standardize a variable with a define mean


From   Maarten Buis <maartenlbuis@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: How to standardize a variable with a define mean
Date   Wed, 1 Feb 2012 10:48:07 +0100

On Wed, Feb 1, 2012 at 10:44 AM, Alberto R Osella wrote:
> I want to standardize a variable (BMI) with a given mean value. I've
> obtained that value from a -summarize- command, that is r(mean).
> Now I want to pass the value of r(mean) to the egen command. Here the
> commands and the error returned by Stata.
>
> . sum BMI
> . scalar meanbmi=r(mean)
> . display meanbmi
> 25.8435
> . egen stdbmi=std(BMI), mean(meanbmi) std(1)
> option mean() incorrectly specified
> r(198);

try:

egen stdbmi=std(BMI), mean(`=meanbmi') std(1)

The trick is that meanbmi is the name of a scalar while the -mean()-
option expects a number. By surrounding that scalar name with " `= "
and " ' " you are forcing Stata to first evaluate the scalar name,
resulting in a number, which is exactly what the -mean()- option
wanted.

Hope this helps,
Maarten


--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany


http://www.maartenbuis.nl
--------------------------
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