HI,
You can also use these in addition to aggregate:
tapply(dat$x,INDEX=dat[grp],mean)
library(plyr)
ddply(dat,.(dat[grp]$a,dat[grp]$d),summarize,mean(x))
# dat[grp]$a dat[grp]$d ..1
#1 b c 0.26781378
#2 b d -0.01994023
#3 c e 0.14874737
#4 d d -0.21051512
#5 e b 0.18821072
A.K.
----- Original Message -----
From: Xianming Wei <x...@bses.com.au>
To: "r-help@r-project.org" <r-help@r-project.org>
Cc:
Sent: Thursday, August 30, 2012 10:37 PM
Subject: [R] dynamic list in aggregate()
Hi all,
How can I have a dynamic list for different combinations of grouping factors in
the following example? Thanks.
dat <- data.frame(x=rnorm(100),
a=sample(letters[1:5], replace = T),
b=sample(letters[1:5], replace = T),
c=sample(letters[1:5], replace = T),
d=sample(letters[1:5], replace = T))
## define grouping factors
grp <- c('a','d') # or any combination among a, b, c and d
## something like this for the list
lst <- paste('dat$', grp, sep='', collapse =',')
## aggregate on the defined list
aggregate(dat$x, list(lst), mean)
Thanks.
Regards,
Xianming
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