Here's one attempt with plyr, hopefully Hadley will give you a better solution ( I could not get cast() to do it either)

test <- data .frame (a=c("A","A","A","A","B","B","B"),b=c(1,1,2,2,1,1,1),c=sample(1:7))
ddply(test,.(a,b),.fun=function(.) paste(.)[3])

  a b         V1
1 A 1    c(2, 4)
2 B 1 c(7, 1, 6)
3 A 2    c(3, 5)

# note that with your example R seems to use some magic
test <-
data.frame(a=c("A","A","A","A","B","B","B"),b=c(1,1,2,2,1,1,1),c=1:7)


  a b  V1
1 A 1 1:2
2 B 1 5:7
3 A 2 3:4

I have no idea how this happens!


HTH,

baptiste



On 6 Apr 2009, at 15:38, Daniel Brewer wrote:

Hello,

I would like to reshape my data for presentation purposes from something
like this:
test <-
data.frame(a=c("A","A","A","A","B","B","B"),b=c(1,1,2,2,1,1,1),c=1:7)
test
 a b c
1 A 1 1
2 A 1 2
3 A 2 3
4 A 2 4
5 B 1 5
6 B 1 6
7 B 1 7

to something like this:
 a b c
1 A 1 1,2
3 A 2 3,4
5 B 1 5,6,7

This seems to be the sort of the thing that the reshape library should
be able to do, but I just can't work out how to do it.

Many thanks

Dan

--
**************************************************************
Daniel Brewer, Ph.D.

Institute of Cancer Research
Molecular Carcinogenesis
Email: daniel.bre...@icr.ac.uk
**************************************************************

The Institute of Cancer Research: Royal Cancer Hospital, a charitable Company Limited by Guarantee, Registered in England under Company No. 534147 with its Registered Office at 123 Old Brompton Road, London SW7 3RP.

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