"David Orme" <[EMAIL PROTECTED]> wrote: ... > I'm have a list of integer vectors and I want to perform an outer() > like operation on the list. As an example, take the following list: > > mylist <- list(1:5,3:9,8:12) > > A simple example of the kind of thing I want to do is to find the sum > of the shared numbers between each vector to give a result like: > > result <- array(c(15,12,0,12,42,17,0,17,50), dim=c(3,3)) > > Two for() loops is the easiest way but I wondered if there was a > neater/faster solution. > > mylist.len <- length(mylist) > ind <- 1:mylist.len > result <- array(NA, dim=c(mylist.len,mylist.len)) > for(x in ind){ > for(y in ind){ > result[x,y] <- sum(mylist[[x]][test[[x]] %in% test[[y]]]) > } > } >
I'm having a hard time figuring out what you want. Who is this mystery object "test"? When I drop "test" from the text, and use: result[x,y] <- sum(mylist[[x]] %in% mylist[[y]]) It doesn't give a syntax error, but the result is nothing like the one you posted above. As a style point, ind <- seq(along=mylist) is a bit more foolproof in the case of empty lists being accidentally passed to the code (been bitten that way once or twice). Cheers Jason ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html