Here we go again: append an element to a list in R

Question

I am not happy with the accepted answer to Append an object to a list in R in amortized constant time?

> list1 <- list(\"foo\", pi)
> bar <- list         


        

Answer 1

Operations that change the length of a list/vector in R always copy all the elements into a new list, and so will be slow, O(n). Storing in an environment is O(1) but has a higher constant overhead. For an actual O(1) append and benchmark comparison of a number of approaches see my answer to the other question at https://stackoverflow.com/a/32870310/264177.