is there a way to extend LETTERS past 26 characters e.g., AA, AB, AC…?

Question

I use LETTERS most of the time for my factors but today I tried to go beyond 26 characters:

LETTERS[1:32]

Expecting there to be an automati

Answer 1

This solution uses recursion. Usage is a bit different in the sense MORELETTERS is not a long vector you will have to store and possibly expand as your inputs get larger. Instead, it is a function that converts your numbers into the new base.

extend <- function(alphabet) function(i) {
   base10toA <- function(n, A) {
      stopifnot(n >= 0L)
      N <- length(A)
      j <- n %/% N 
      if (j == 0L) A[n + 1L] else paste0(Recall(j - 1L, A), A[n %% N + 1L])
   }   
   vapply(i-1L, base10toA, character(1L), alphabet)
}
MORELETTERS <- extend(LETTERS)         

MORELETTERS(1:1000)
# [1] "A" "B" ... "ALL"
MORELETTERS(c(1, 26, 27, 1000, 1e6, .Machine$integer.max))
# [1] "A"       "Z"       "AA"      "ALL"     "BDWGN"   "FXSHRXW"