[R] Applying "by" results

[Dieter Menne]

I want to subtract the group minumum of the value in each group
from the indidvidual values, replacing the original values of Press
(something like a groupwise sweep).

This almost works:

#-----------------------------------
PPress<-data.frame(Marker=as.factor(c(rep(1,12),rep(2,12))),
                   Chan=as.factor(rep(1:4,6)), Press=rnorm(24) )
attach(PPress)
by (Press,list(Marker,Chan), function(x) x-min(x))
#-------------------------------------

The data printed out those I need, but how do I
get these back into to PPress?


---------------------------------------
Dr. Dieter Menne
Biomed Software
72074 Tübingen
Tel (49) (7071) 52176
FAX (49) (7071) 55 10 46
dieter.menne at menne-biomed.de
www.menne-biomed.de

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