R/interleave.R

In soodoku/guess: Adjust Estimates of Learning for Guessing

#' Interleave
#'
#' Used Internally
#' Interleave two character vectors. The output is a vector. The first entry is from the first vector.
#' Vectors can be of different lengths. If one is shorter than the other, entries of unmatched longer vector are left un-interleaved.  
#' @param vec1 first vector
#' @param vec2 second vector
#' @return interleaved vector
#' # t1 <- paste0("t1", letters[1:5]); t2 <- paste0("t2", letters[1:5]); interleave(t1, t2)

interleave <- function(vec1, vec2) {

  if (!is.vector(vec1, mode = "character") |
        !is.vector(vec2, mode = "character")) {
          stop("Either or both of the inputs are not a character vector.\n
               The function only takes character vectors.")
  }

  if (length(vec1) != length(vec2)) {
    warning("Vectors are of different lengths. Unmatched entries of the
            longer vector will be left un-interleaved.\n")
  }

  ord1 <- 2 * (1:length(vec1)) - 1
  ord2 <- 2 * (1:length(vec2))

  c(vec1, vec2)[order(c(ord1, ord2))]
}