private String printContingencyMatrix() {
    String s = "";
    if (results.size() > 0) {
      s += String.format(" %1$10s", "");
      for (String c : results.get(0).getClassNames()) {
        s += String.format("%1$6s ", c.substring(0, Math.min(5, c.length())));
      }
      s += "\n";
      for (String c1 : results.get(0).getClassNames()) {
        s += "-" + String.format("%1$10s ", c1);
        for (String c2 : results.get(0).getClassNames()) {
          int count = 0;
          for (EvaluationResults result : results) {
            try {
              count += result.getInstances(c1, c2);
            } catch (AuToBIException e) {
              AuToBIUtils.error("FATAL EROR: Inconsistent EvaluationSummary.");
              return s;
            }
          }
          s += String.format("%1$6d ", count);
        }
        s += "\n";
      }
    }
    return s;
  }