Numbers into English Words"
In english: Translate Integers into English

knitr::opts_chunk$set(collapse = TRUE,
                      comment = "")
library(english)

Genesis and development

In answer to a question on R-help John Fox provided an elegant R function to translate integers into English numbers. The present package extends this code to an S3 class, with constructor functions and methods to make this original idea more conveniently available.

The function as.english is intended to provide a parallel facility to the function as.roman in the utils package.

The main purpose of the package is to present an interesting programming example rather than to solve a likely real problem, though there could well be some applications in unusual contexts.

Note added in Version 1.1-4. The two small helper functions words and Words are included to facilitate inline code inserts in R markdown files. See the help files for examples. The ordinal function produces character strings and may be used directly in inline code inserts. Use `r '\x60r words(103)\x60'` rather than `r '\x60r english(103)\x60'` in R markdown files.

Note added in Version 1.2-0. The function indefinite added for algorithmically including an apprporiate indefinite article in a document insert. Based on a suggestion of Anne Pier Salverda.

The capitalised version, Indefinite, was added in 1.2-1.

This vignette was added in 1.2-2.

Examples

The main use envisaged for these tools is for code inserts in either R markdown or R noweb documents. It is easier here to demonstrate their function in plain code chunks, as below.

The resolution of an integer into words depends on the style of English chosen. English (UK) style inserts the conjunction and in various places where American (USA) style omits it. Wheter or not this happens is governed by the english.UK option, (a logical variable, TRUE for UK English), but if this option is unset, a guess is made as to which style is needed depending on the user's locale.

soldiers <- 10006
oldOpt <- options(english.UK = TRUE)
cat("The Duke of York had approximately", words(soldiers), "men.\n")
cat("How many did you say?  ", Words(soldiers), ", approximately.\n", sep = "")

options(english.UK = FALSE)
cat("The Duke of York had approximately", words(soldiers), "men.\n")
cat("How many did you say?  ", Words(soldiers), ", approximately.\n", sep = "")
options(oldOpt)

Ordinal numbers are handled as well.

days <- 1:6
cat(paste("\nOn the", ordinal(days), "day of Christmas..."))

The indefinite article, "a" or "an", can be algorithmically chosen and prepended, either in lower case or capitalised:

steps <- 7:11
cat(paste0("\nThis is ", indefinite(steps), "-step process..."))
cat(paste0("\nThis is ", indefinite(steps, words = FALSE), "-step process..."))
cat(paste0("\n", Indefinite(ordinal(steps)), " step of the process is..."))

Roman notation is provided by the utils::as.roman function in a similar way:

numbers <- c(1:10, 1999, 2019)
punct <- c(rep(",", 10), " and",".")
cat(c("In Roman notation:", 
      paste0("\n\t", Words(numbers), " is written as \"",
             utils::as.roman(numbers),"\"", punct)))
cat("\nDoing arithmetic in Roman notation can be difficult.")