Chaining list of vectors - r

Question

If I have a list of vectors such as below
list.x <- list(1:2, 1:3, 3:4, 5, 5:6)
Is there a way to replace each list element with an element that includes all the other values that the element can be paired with?
For example the first element (list.x[[1]]) would be replace with 1:4 because element 2 (list.x[[2]]) shows that 2, is also paired with 3, and element 3 shows that 3 is also paired with 4.
The final result I would like to achieve would be this list
final.list <- list(1:4, 1:4, 1:4, 5:6, 5:6)

Answer 1

I needed a change of pace today, so I decided to try to answer the question using base R. Here it goes:
First, I created a function that unions two vectors if they intersect, and if not, simply returns the first vector:
expand.if.toucing <- function(vector1, vector2) {
i = intersect(vector1, vector2);
if (NROW(i) > 0)
union(vector1, vector2)
else
vector1;
}
Then I made a function that merges one element in the list of vectors with another:
list.reduce <- function (lst) {
for(v1 in 1:NROW(lst))
for (v2 in 1:NROW(lst)) {
if (v1 == v2)
next;
prevLength <- NROW(lst[[v1]]);
lst[[v1]] <- expand.if.toucing(lst[[v1]], lst[[v2]]);
newLength <- NROW(lst[[v1]]);
if (newLength == prevLength)
next;
return(lst[-v2]);
}
lst;
}
After this, I made a function that merges all vectors in the list that can be merged. This is sort of a proto cluster analysis, so I called it clusterize:
clusterize <- function (lst) {
reduced = TRUE;
while(reduced) {
prevLength <- NROW(lst);
lst <- list.reduce(lst);
newLength <- NROW(lst);
reduced <- prevLength != newLength;
}
lst;
}
Now it's just a matter of replacing each element in the original list with its associated cluster:
replace.with.clusters <- function(lst, clusters) {
for(l in 1:NROW(lst))
for(c in 1:NROW(clusters)) {
lst[[l]] <- expand.if.toucing(lst[[l]], clusters[[c]]);
next;
}
lst;
}
You're good to go. The two main functions are clusterize and replace.with.cluster. Use them like this:
list.x <- list(1:2, 1:3, 3:4, 5, 5:6)
clusters <- clusterize(list.x);
replace.with.clusters(list.x, clusters);
# Outputs the following:
#
# [[1]]
# [1] 1 2 3 4
#
# [[2]]
# [1] 1 2 3 4
#
# [[3]]
# [1] 3 4 1 2
#
# [[4]]
# [1] 5 6
#
# [[5]]
# [1] 5 6
The third element is in a different order than your list, but from the way you describe the problem, order is not truly relevant.