[R] standardising a data matrix

[Martyn Plummer]

On 02-Mar-01 Tord Snall wrote:
> Dear all,
> I would like to standardise my data. Here is an exemple for two columns:
> 
>> onorm<- read.table("onorm.txt", header=T)
>> names(onorm)
> [1] "on1" "on2" "on3" "on4" "on5"
>> norm<- data.frame((onorm$on1-mean(onorm$on1))/stdev(onorm$on1),
> (onorm$on2-mean(onorm$on2))/stdev(onorm$on2))
> 
> I would be happy however not having got to do this coulumnwise since I have
> about 80 columns. Could someone please give a hint on how to do this for
> the whole matrix. 

Use sweep() 

norm <- sweep(onorm, 2, apply(onorm, 2, mean), "-") # standardize mean to 0
norm <- sweep(norm, 2, apply(norm, 2, sd), "/")   # standardize variance to 1

> The names of the coulumns are on1, on2 etc. as above. I want the columns in
> the new standardised dataset to have the names son1, son2 etc, i.e. adding
> an s to all the original column names. How do I do that?

names(norm) <- paste("s", names(norm), sep="")

Martyn

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