A really simple sentiment analysis function implemented in R that illustrates some of the nifty features of the R language.

sentiment.r

sentiment <- function(str, words, weights=NULL) {
  if (is.null(weights)) {
    weights <- rep(1, length(words))
  }
  
  if (length(words) != length(weights)) {
    stop('Length of words and weights not equal')
  }
  
  str.wts <- rep(0, length(str))
  
  for (i in 1:length(words)) {
    cts <- str_count(str, words[[i]])
    str.wts <- str.wts + (cts * weights[[i]])
  }
  
  str.wts
}