Thank you Jorge, this is exactly what I needed!
Another solution that works too, suggested by Steve:group.med <- tapply( rt,
list(group, session), median)
From: jorgeivanve...@gmail.com
Date: Wed, 8 Dec 2010 09:43:47 -0500
Subject: Re: [R] How can I calculate the median for each factor combination?
To: mariannestep...@hotmail.com
CC: r-help@r-project.org
Hi Marianne,
Please consider the following:
with(table, aggregate(rt, list(group, session), FUN = median))
HTH,Jorge
On Wed, Dec 8, 2010 at 9:29 AM, Marianne Stephan <> wrote:
Hello everybody,
I would like to calculate the median for each factor combination, with only one
value per factor combination as an output.
Could anybody help me?
For example:
# make table
g<-1:2
group<-rep(g, each=5)
session<-c(1,1,2,2,2,1,1,1,2,2)
rt<-seq(length=10,300, 800)
rt<-round(rt, digits=2)
table<-data.frame(group, session, rt)
table
á group session á á rt
1 á á á1 á á á 1 300.00
2 á á á1 á á á 1 355.56
3 á á á1 á á á 2 411.11
4 á á á1 á á á 2 466.67
5 á á á1 á á á 2 522.22
6 á á á2 á á á 1 577.78
7 á á á2 á á á 1 633.33
8 á á á2 á á á 1 688.89
9 á á á2 á á á 2 744.44
10 á á 2 á á á 2 800.00
Besides others I tried the following:
median<-ave(rt, group, session, FUN=median)
median<-frameApply(table,by=c("group", "session"), on="rt", fun=median)
I would appreciate your help a lot.
Marianne
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