David Orme <[EMAIL PROTECTED]> writes:
> Hi,
>
> 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]]])
> }
> }
>
How about
> mysum <- function(x,y)mapply(function(x,y)sum(intersect(x,y)),x,y)
> outer(l,l,mysum)
[,1] [,2] [,3]
[1,] 15 12 0
[2,] 12 42 17
[3,] 0 17 50
(notice that your problem really isn't that you have a list, but that
you have functions that don't vectorize over lists.)
--
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907
______________________________________________
[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
