How to paste two vectors together and pad at the end?

Question

I would like to paste two character strings together and pad at the end with another character to make the combination a certain length. I was wondering if there was an option to paste that one can pass or another trick that I am missing? I can do this in multiple lines by figuring out the length of each and then calling paste with rep(my_pad_character,N) but I would like to do this in one line.

Ex: pad together "hi", and "hello" and pad with an "a" to make the sequence length 10. the result would be "hihelloaaa"

Answer 1

Here is one option:

s1 <- "hi"
s2 <- "hello"

f <- function(x, y, pad = "a", length = 10) {
   out <- paste0(x, y)
   nc <- nchar(out)
   paste0(out, paste(rep(pad, length - nc), collapse = ""))
}

> f(s1, s2)
[1] "hihelloaaa"