Massimiliano -
Here's one way, assuming you wanted b to be the same
length as a:
df = transform(df,b=ave(as.character(df$a),df$ID,
FUN=function(a)paste(a,collapse='')))
If you just want one observation for each value of ID, you
could use
aggregate(df$a,list(ID=df$ID),paste,collapse='')
- Phil Spector
Statistical Computing Facility
Department of Statistics
UC Berkeley
spec...@stat.berkeley.edu
On Wed, 27 Apr 2011, Massimiliano Tripoli wrote:
Dear all,
I have the following R dataframe:
set.seed(11)
(df <- data.frame(ID=rep(1:10,1:10),a=factor(sample(1:4,55,rep=T)) ))
where ID is an identification code.
I need to create a new variable "b" in which I would paste the full group
of "a" variable according to ID variable.
For example for ID=2 "b" should be 13, for ID=3 "b" should be 114, and
for ID=4 should be 1241.
How can I do that ?
Thank you for any advices,
Regards,
Massimiliano Tripoli
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