# File lib/classifier/lsi.rb, line 272
    def highest_ranked_stems( doc, count=3 )
      raise "Requested stem ranking on non-indexed content!" unless @items[doc]
      arr = node_for_content(doc).lsi_vector.to_a
      top_n = arr.sort.reverse[0..count-1]
      return top_n.collect { |x| @word_list.word_for_index(arr.index(x))}
    end