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


From   Alberto R Osella <arosella@irccsdebellis.it>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: How to standardize a variable with a define mean
Date   Wed, 01 Feb 2012 11:05:45 +0100

Thanks Maarten. It works!!!!

Alberto R. Osella, MD, PhD
Laboratorio di Epidemiologia e Biostatistica
IRCCS Saverio de Bellis
Via Turi, 27
70013 Castellana Grotte (BA)
Italia
Tel:    +39 0804994655
Fax:    +39 0804994650
e-mail: arosella@irccsdebellis.it


Il 01/02/2012 10:48, Maarten Buis ha scritto:
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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