outer() equivalent for non-vector lists in R

Question

I understand how outer() works in R:

> outer(c(1,2,4),c(8,16,32), \"*\")

     [,1] [,2] [,3]
[1,]    8   16   32
[2,]   16   32   64
[3,]   32   64  128
         


        

Answer 1

Although this is an old question, here is another solution that is more in the spirit of the outer function. The idea is to apply outer along the indices of list1 and list2:

cor2 <- Vectorize(function(x,y) {
   vec1 <- list1[[x]]
   vec2 <- list2[[y]]
   cor(vec1,vec2,method="spearman")
})
outer(1:length(list1), 1:length(list2), cor2)