R help - Oct 2011 - new standardised variable based on group membership

Hi
I have a data comprised of repeated measures of growth (5-15 records per
individual) for 580 fish (similar to Orange dataset from nlme library). I would
like to standardise these growth measures (yi – ŷ/sd) using mean and standard
deviation unique to each fish. Can someone suggest a function that would help me
do this? I’ve had a look at scale and sweep but can’t find a worked example that
does what I’m after

Cheers

John


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Dear John,

You need to combine scale with a grouping function.

data(Orange)
library(plyr)
Orange <- ddply(Orange, .(Tree), function(x){
	x$ddplyAge <- scale(x$age)[, 1]
	x
})

Orange$aveAge <- ave(Orange$age, by = Orange$Tree, FUN = scale)

all.equal(Orange$ddplyAge, Orange$aveAge)

Best regards,

Thierry

> -----Oorspronkelijk bericht-----
> Van: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org]
> Namens John.Morrongiello at csiro.au
> Verzonden: maandag 3 oktober 2011 7:34
> Aan: r-help at r-project.org
> Onderwerp: [R] new standardised variable based on group membership
> 
> Hi
> I have a data comprised of repeated measures of growth (5-15 records per
> individual) for 580 fish (similar to Orange dataset from nlme library). I
would like
> to standardise these growth measures (yi ? ?/sd) using mean and standard
> deviation unique to each fish. Can someone suggest a function that would
help
> me do this? I?ve had a look at scale and sweep but can?t find a worked
example
> that does what I?m after
> 
> Cheers
> 
> John
> 
> 
> 	[[alternative HTML version deleted]]