[R] Question about collapse/aggregate and avoidance of loops

[Weiss, Bernd]

Dear all,

given the following data

## original data
id <- c(1,1,1,2,2,3)
author <- c("A","B","C","D","E","F")
tmp <- data.frame(id,author)
tmp


 > tmp
   id author
1  1      A
2  1      B
3  1      C
4  2      D
5  2      E
6  3      F

What is the best (most efficient/vectorized/avoiding loops) approach to 
obtain the following data frame?

id 	author
1	"A, B, C"
2 	"D, E"
3	"F"


Thanks for your help,

Bernd





 > version
                _
platform       i386-pc-mingw32
arch           i386
os             mingw32
system         i386, mingw32
status         Patched
major          2
minor          8.1
year           2008
month          12
day            22
svn rev        47296
language       R
version.string R version 2.8.1 Patched (2008-12-22 r47296)