Transpose/reshape rows in columns with given conditions

Question

I have the following data:

request   user   group
1         1      1
4         1      1
7         1      1
5         1      2
8         1      2
1         2              


        

Answer 1

library(reshape)

# Make some fake data
dat <- data.frame(user = c(1,1,1,2,2,3), group = c(1,1,1,1,1,2), request = c(1,4,7,5,8,1))
# Add in an ordered id
newdat <- ddply(dat, .(user, group), transform, idx = paste("request", 1:length(request), sep = ""))
# Use cast to get what we want
cast(newdat, user + group ~ idx, value = .(request))

There is probably a nicer way to get what I call idx which is essentially what becomes the column title. It might be possible to do this without creating the newdat data set but this is what I thought of.