[R] scaling-centering a vector using an index

[Peter Dalgaard BSA]

Thomas de Cornulier <oedic at cebc.cnrs.fr> writes:

> dear all,
> I would like to center and scale some columns of a data frame (these
> include NAs) according to the levels of an index (list of factors from
> the same data frame).
> I tried to code it using for loops but gave up. I guess there is a
> straightforward way to achieve this: any hint welcome!
> thanks a lot
> thomas

Erm, define "according to the levels of" or have a look at the
examples for split/unsplit and see whether you mean what I think you
mean....

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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