[R] Scalling/Centering the Data by an Index

From: Ashraf Chaudhary <mchaudha_at_jhsph.edu>
Date: Thu 13 Jul 2006 - 16:43:08 EST


Dear All:
I would like to center the data in 'x' by 'group'. The following code scale the data and I have not been able to figure out how to change it so I get the centered data.  

x <- c(1, 2, 3, 4, 5, 6, 7, 8)
group <- c(1,1,1,2,2,2,2,2)
unsplit(lapply(split(x,group),scale),group)

I would appreciate your help.  

Ashraf

-----------------______________________________________
M. Ashraf Chaudhary, Ph.D.
Associate Scientist/Biostatistician
Department of International Health
Johns Hopkins Bloomberg School of Public Health 615 N. Wolfe St. Room W5506
Baltimore MD 21205-2179

(410) 502-0741/fax: (410) 502-6733
 <mailto:mchaudha@jhsph.edu> mchaudha@jhsph.edu Web:
http://faculty.jhsph.edu/?F=Mohammad&L=Chaudhary  

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