add add_s

[trinker]

add_s <- function (x, keep.original = TRUE) {
    ends <- qdapRegex::pastex(c("s$", "x$", "ch$", "sh$"))
    pluralify <- ifelse(grepl(ends, x), "es", "s")
    c(if (keep.original) {
        x
    }, gsub("ys$", "ies", paste0(x, pluralify)))
}

[trinker]

Add handling for irregular nouns http://www.esldesk.com/vocabulary/irregular-nouns and http://www.ef.edu/english-resources/english-grammar/singular-and-plural-nouns/

#' Make Plural (or Verb to Singular) Versions of Words
#' 
#' Add -s, -es, or -ies to words.
#' 
#' @param x A vector of words to make plural.
#' @param keep.original logical.  If \code{TRUE} the original words are kept in 
#' the return vector.
#' @return Returns a vector of plural words.
#' @keywords plural
#' @export
#' @examples 
#' 
x <- c('fox', 'sky', 'dog', 'church', 'fish', 'miss', 'mitch')
make_plural(x)
make_plural <- function (x, keep.original = FALSE) {
    ends <- "(sh?|x|z|ch)$"
    pluralify <- ifelse(grepl(ends, x), "es", "s")
    c(if (keep.original) {
        x
    }, gsub("ys$", "ies", paste0(x, pluralify)))
}