R/numbers2words.R

In jaspercooper/surveybuilder:

#' Convert numbers to english words
#'
#' @param x A number
#' @return A number spelled out in English words
#' @export
numbers2words <- function(x) {
  # Credit to John Fox 2005 for this function
  helper <- function(x) {
    digits <- rev(strsplit(as.character(x), "")[[1]])
    nDigits <- length(digits)
    if (nDigits == 1)
      as.vector(ones[digits])
    else if (nDigits == 2)
      if (x <= 19)
        as.vector(teens[digits[1]])
    else
      trim(paste(tens[digits[2]],
                 Recall(as.numeric(digits[1]))))
    else if (nDigits == 3)
      trim(paste(ones[digits[3]], "hundred",
                 Recall(makeNumber(digits[2:1]))))
    else {
      nSuffix <- ((nDigits + 2) %/% 3) - 1
      if (nSuffix > length(suffixes))
        stop(paste(x, "is too large!"))
      trim(paste(Recall(makeNumber(digits[nDigits:(3 * nSuffix + 1)])),
                 suffixes[nSuffix],
                 Recall(makeNumber(digits[(3 * nSuffix):1]))))
    }
  }
  trim <- function(text) {
    gsub("^\ ", "", gsub("\ *$", "", text))
  }
  makeNumber <-
    function(...)
      as.numeric(paste(..., collapse = ""))
  opts <-
    options(scipen = 100)
  on.exit(options(opts))
  ones <-
    c("", "one", "two", "three", "four", "five", "six", "seven",
      "eight", "nine")
  names(ones) <- 0:9
  teens <-
    c(
      "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen",

      "sixteen", " seventeen", "eighteen", "nineteen"
    )
  names(teens) <- 0:9
  tens <-
    c("twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty",

      "ninety")
  names(tens) <- 2:9
  x <- round(x)
  suffixes <-
    c("thousand", "million", "billion", "trillion")
  if (length(x) > 1)
      return(sapply(x, helper))
  helper(x)
}