That makes sense, so I can do something like,
count <- function(x){
as.integer(unclass(table(x)))
}
count(d$user_id)
ddply(d, .(user_id), transform, count = count(user_id))
user_id website time count
1 20 google 930 2
2 20 facebook 1000 2
3 21 yahoo 935 1
4 25 facebook 1015 1
5 61 google 940 1
Have I missed a built-in function to obtain this result?
Thanks,
baptiste
On 3 Apr 2009, at 14:16, hadley wickham wrote:
On Fri, Apr 3, 2009 at 4:43 AM, baptiste auguie <ba...@exeter.ac.uk>
wrote:
Dear all,
I'm puzzled by the following example inspired by a recent question on
R-help,
cc <- textConnection("user_id website time
20 google 0930
21 yahoo 0935
20 facebook 1000
25 facebook 1015
61 google 0940")
d <- read.table(cc, head=T) ; close(cc)
table(d$user_id) # count the occurrences
# now I'd like to include these results in the original data.frame,
ddply(d, .(website), transform, count = table(user_id)) # why two new
columns?
Because ddply expects a data frame as output from your aggregation
function. When the output isn't a data frame, it calls as.data.frame,
which in this case produces a data frame with two columns.
Hadley
--
http://had.co.nz/
_____________________________
Baptiste Auguié
School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK
Phone: +44 1392 264187
http://newton.ex.ac.uk/research/emag
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