I want a vector with the excel-letters: c(A, B, C, … Z, AA, AB, … AZ, BA, …).
My try was this:
excel_letters <- LETTERS
for(n in length(LETTERS)){
excel_letters <- c(excel_letters, paste0(LETTERS[n], LETTERS))
}
Since i am defining excel_letters outside of the loop before iterating through the loop, i expected to get the wanted output. Instead i am only getting:
[1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y" "Z" "ZA" "ZB" "ZC"
[30] "ZD" "ZE" "ZF" "ZG" "ZH" "ZI" "ZJ" "ZK" "ZL" "ZM" "ZN" "ZO" "ZP" "ZQ" "ZR" "ZS" "ZT" "ZU" "ZV" "ZW" "ZX" "ZY" "ZZ"
Which is basically LETTERS plus the last iteration.
What am i missing here?
I know there are other approaches to this but i wanna know why this specifically doesn’t work.
>Solution :
As mentioned, length(LETTERS) is a single element, so for (n in length(LETTERS)) iterates over a single value.
In general you rarely need to iterate over indices — it’s easier to iterate over the values in your vector directly:
for (letter in LETTERS) …
In the rare event where you really need to iterate over the indices of a vector (which you don’t need here), use the pattern
for (i in seq_along(the_vector))
… but for your use-case, a better (shorter, more expressive, more efficient) solution avoids the loop entirely, in favour of direct construction:
excel_letters <- paste0(rep(c("", LETTERS), each = length(LETTERS)), LETTERS)
The more you write R the more you will discover how vectorisation and bespoke algorithms allow you to avoid loops.