[R] Centering data frame by factor

[Daniel Malter]

P1-tapply(P1,Experiment,mean)[Experiment]

HTH,
Daniel


ronny wrote:
> 
> Hi,
> 
> I would like to center P1 and P2 of the following data frame by the factor
> "Experiment", i.e. substruct from each value the average of its
> experiment, and keep the original data structure, i.e. the experiment and
> the group of each value. 
> 
> RAW=
> data.frame("Experiment"=c(2,2,2,1,1,1),"Group"=c("A","A","B","A","A","B"),"P1"=c(10,12,14,5,3,4),"P2"=c(8,12,16,2,3,4))
> 
> Desired result:
> 
> NORMALIZED=
> data.frame("Experiment"=c(2,2,2,1,1,1),"Group"=c("B","A","B","B","A","B"),"P1"=c(-2,0,2,1,-1,0),"P2"=c(-4,0,4,-1,0,1))
> 
> I tried using "by", but then I lose the original order, and the "Group"
> varaible. Can you help?
> 
>> RAW 
>   Experiment Group P1 P2
>          2     A 10  8
>          2     A 12 12
>          2     B 14 16
>          1     A  5  2
>          1     A  3  3
>          1     B  4  4
> 
> NOT.OK<- within (RAW,
> {P1<-do.call(rbind,by(RAW$P1,RAW$Experiment,scale,scale=F))})
> 
>> NOT.OK
>   Experiment Group P1 P2
>           2     A  1  8
>           2     A -1 12
>           2     B  0 16
>           1     A -2  2
>           1     A  0  3
>           1     B  2  4
> 

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