R/get_common_words.R

In dtburk/texanaaid: An Aide for Text Analysis

#' Get common words
#'
#' Get the most frequent words in a group of documents.
#' @param prob_mtrx A matrix with (named) columns for words, and rows for either
#'   documents or document groups. If each row represents a document,
#'   \code{group_membership} must be provided.
#' @param group_num An integer corresponding to the document group of interest.
#' @param n An integer specifying how many words should be returned.
#' @param group_membership An integer vector specifying the group membership of
#'   documents in \code{prob_mtrx}.
#' @export

get_common_words <- function(prob_mtrx, group_num, n, group_membership=NULL) {
  if(!is.null(group_membership)) {
    focal_docs <- prob_mtrx[group_membership == group_num, , drop=FALSE]
    focal_probs <- apply(focal_docs, 2, mean)
  } else {
    focal_probs <- prob_mtrx[group_num, ]
  }
  return(names(sort(focal_probs, decreasing=TRUE))[1:n])
}