R/numbers2words.R

In JVAdams/jvamisc: A Collection of Utility Functions

#' Convert Integers to Words
#'
#' Convert integers into English words.
#' @param x
#'   An integer vector to be converted.
#' @param billion
#'   A character scalar indicating if "US" (default) or "UK" meaning of
#'   billion should be used.
#' @param and
#'   A character scalar for use as a conjunction, set to "" when
#'   billion=="US" (default) and "and" otherwise.
#' @return
#'   A character vector, the same length as \code{x} giving the English word(s)
#'   for the integer(s) \code{x}.
#' @export
#' @references
#'   John Fox.  2005.
#'   How Do You Spell That Number?
#'   Rnews Volume 5(1):51-54.
#'   \href{http://cran.r-project.org/doc/Rnews/Rnews_2005-1.pdf}{[link]}.
#' @examples
#' numbers2words(c(4560000000, -123, 1000, 12))

numbers2words <- function(x, billion=c("US", "UK")[1],
    and=if (billion=="US") "" else "and") {
  billion <- match.arg(billion)
  trim <- function(text) gsub("(^\ *)|((\ *|-|,\ zero|-zero)$)", "", text)
  makeNumber <- function(x) as.numeric(paste(x, collapse=""))
  makeDigits <- function(x) strsplit(as.character(x), "")[[1]]
  helper <- function(x){
    negative <- x < 0
    x <- abs(x)
    digits <- makeDigits(x)
    nDigits <- length(digits)
    result <- if (nDigits == 1) as.vector(ones[digits])
    else if (nDigits == 2)
      if (x <= 19) as.vector(teens[digits[2]])
        else trim(paste(tens[digits[1]], "-", ones[digits[2]], sep=""))
    else if (nDigits == 3) {
      tail <- makeNumber(digits[2:3])
      if (tail == 0) paste(ones[digits[1]], "hundred")
      else trim(paste(ones[digits[1]], trim(paste("hundred", and)),
        helper(tail)))
      }
    else {
      nSuffix <- ((nDigits + 2) %/% 3) - 1
      if (nSuffix > length(suffixes) || nDigits > 15)
        stop(paste(x, "is too large!"))
      pick <- 1:(nDigits - 3*nSuffix)
      trim(paste(helper(makeNumber(digits[pick])), suffixes[nSuffix],
        helper(makeNumber(digits[-pick]))))
      }
    if (billion == "UK"){
      words <- strsplit(result, " ")[[1]]
      if (length(grep("million,", words)) > 1)
        result <- sub(" million, ", ", ", result)
      }
    if (negative) paste("minus", result) else result
    }
  opts <- options(scipen=100)
  on.exit(options(opts))
  ones <- c("zero", "one", "two", "three", "four", "five", "six", "seven",
    "eight", "nine")
  teens <- c("ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen",
    "sixteen", "seventeen", "eighteen", "nineteen")
  names(ones) <- names(teens) <- 0:9
  tens <- c("twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty",
    "ninety")
  names(tens) <- 2:9
  suffixes <- if (billion == "US")
    c("thousand,", "million,", "billion,", "trillion,")
    else
    c("thousand,", "million,", "thousand million,", "billion,")
  x <- round(x)
  if (length(x) > 1) sapply(x, helper) else helper(x)
  }