One approach is the following:
Dat <- read.table(textConnection(
"Jim A
Bob A
Bob C
Larry D
Alice C
Tom F
Tom D
Tom A
Alice B
Nancy B"))
closeAllConnections()
names(Dat) <- c("name", "act")
out <- tapply(as.character(Dat$name), Dat$act, function (x) {
if (length(x) < 2) c(x, "") else t(combn(x, 2))
})
unique(do.call(rbind, out))
I hope it helps.
Best,
Dimitris
On 3/18/2010 6:05 AM, duncandonutz wrote:
I know one of R's advantages is it's ability to index, eliminating the need
for control loops to select relevant data, so I thought this problem would
be easy. I can't crack it. I have looked through past postings, but
nothing seems to match this problem
I have a data set with one column of actors and one column of acts. I need
a list that will give me a pair of actors in each row, provided they both
participated in the act.
Example:
The Data looks like this:
Jim A
Bob A
Bob C
Larry D
Alice C
Tom F
Tom D
Tom A
Alice B
Nancy B
I would like this:
Jim Bob
Jim Tom
Bob Alice
Larry Tom
Alice Nancy
The order doesn't matter (Jim-Bob vs. Bob-Jim), but each pairing should be
counted only once.
Thanks!
--
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center
Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014
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