code: public double precision() {
      if(!isBinary())throw new UnsupportedOperationException("precision is only implemented for 2 class problems.");
      if(tooLarge())throw new UnsupportedOperationException("precision cannot be computed: too many classes");
      double tp = _cm[1][1];
      double fp = _cm[0][1];
      return tp / (tp + fp);
    }
docs: The percentage of positive predictions that are correct.
  @return Precision