[R] equivalent of group command of the egen function in Stata

[arun]

Hi,
Try this:
#changed data to dat1
 list1<-split(dat1,list(dat1$dim1,dat1$dim2,dat1$dim3))
names(list1)<-1:length(list1)
 res<-do.call(rbind,lapply(list1,function(x) data.frame(x,group=names(list1)[match.call()[[2]][[3]]])))
 row.names(res)<-1:nrow(res)

 head(res)
#         var dim1 dim2 dim3 group
#1 0.06896418    x    1    1     1
#2 0.44958942    x    1    1     1
#3 0.08163725    y    1    1     2
#4 0.21945238    y    1    1     2
#5 0.05695142    z    1    1     3
#6 0.36656387    x    2    1     4
A.K.



----- Original Message -----
From: Francesco Sarracino <f.sarracino at gmail.com>
To: r-help at r-project.org
Cc: 
Sent: Monday, December 10, 2012 9:33 AM
Subject: [R] equivalent of group command of the egen function in Stata

Dear R listers,

I am trying to create a new variable that uniquely identifies groups of
observations in a dataset. So far I couldn't figure out how to do this in
R. In Stata I would simply type:
egen newvar = group(dim1, dim2, dim3)


Please, find below a quick example to show what I am dealing with:
I have a dataset with 4 variables:
var <- runif(50)   ## a variable that I want to group
dim1 <- factor(rep(1:3, length.out= 50), labels = c("x","y","z") ) ## 3
variables that should form the groups
dim2 <- rep(1:2, length.out= 50)
dim3 <- rep(1:5, length.out= 50)

data <- data.frame(var, dim1, dim2, dim3)

I am trying to build a fifth one (let's say: group_id) to uniquely identify
groups of observations as defined by dim1, dim2 and dim3, i.e. 30  groups.

can you please help me figuring out how to do it?
thanks in advance,
f.

-- 
Francesco Sarracino, Ph.D.
https://sites.google.com/site/fsarracino/

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