Add "and" to character vector to be used in string contexts such as Rmarkdown documents

add_and.R

add_and <- function(x) {
  if (!(is.character(x))) {
    warning("`x` must be character. coercing to character")
    x <- as.character(x)
  }

  lx <- length(x)
  if (lx == 1) {
    y <- x
  }
  else if (lx == 2) {
    y <- paste(x[1], "and", x[2])
  }
  else {
    y <- c(x[1:lx-1], paste("and", x[lx]))
    y <- paste(y, collapse = ", ")
  }
  return(y)
}