Get first n words from string.R

# function to get the first n words from a string
get_words <- function(strg, n = 3){
    # remove any leading and trailing whitespace
    strg <- trimws(strg)
    # replace all punctuation with space (except apostrophe)
    strg <- gsub(pattern = "[^[:alnum:][:space:]']", replacement = ' ', strg, perl=TRUE)
    # merge multiple spaces to single space
    strg <- gsub(pattern = "(?<=[\\s])\\s*|^\\s+|\\s+$", replacement = "", strg, perl=TRUE)
    # take first n elements when splitting by space
    strg <- strsplit(strg, split=" ", fixed=TRUE)[[1]][1:n]
    # ommit NA elements
    toupper(paste0(strg[!is.na(strg)], collapse=" "))
}
# Useful links:
# http://stackoverflow.com/questions/25707647/merge-multiple-spaces-to-single-space-remove-trailing-leading-spaces
# http://stackoverflow.com/questions/8697079/remove-all-punctuation-except-apostrophes-in-r