code: public void mapColumns() {
              //System.err.print("Patterns found: ");
              //System.err.println(pattern_list.size());
          
              int index = 0;
              //NOTE: occurrences can be used as Sigma X<k,j> when calculating Entropy
              for (InterveningWordsPattern a_pattern : pattern_list.keySet()) {
                  //int val = a_pattern.getOccurrences();
                  //System.err.println(a_pattern.getPattern() + " " + val);
                  matrix_column_map.put(new Integer(index), a_pattern);
                  index++;
                  InterveningWordsPattern b_pattern = new InterveningWordsPattern(a_pattern.getPattern());
                  b_pattern.setOccurrences(a_pattern.getOccurrences());
                  b_pattern.setReverse(true);
                  matrix_column_map.put(new Integer(index), b_pattern);
                  index++;
              }
      }
docs: Maps a list of patterns to the columns of the sparse matrix.  Takes the
  results of {@link #findPattern()} and maps it to the column indeces of a sparse
  matrix.