item1 <- c("dog", "cat", "horse", "cow", "chicken", "sheep")
item2 <- c("cat", "dog", "cow", "horse", "sheep", "chicken")
correlation <- c(2,2,3,3,4,4)

df <- cbind.data.frame(item1, item2, correlation)
df


    item1   item2 correlation
1     dog     cat     2
2     cat     dog     2
3   horse     cow     3
4     cow   horse     3
5 chicken   sheep     4
6   sheep chicken     4

item1   item2 correlation
1     dog     cat     2
2   horse     cow     3
3 chicken   sheep     4