code: public double falsePositiveRate() {
      double fpr = 0;
      for(int i = 0; i < confusion.length; i++) {
        fpr += falsePositiveRate(i) * colSum(i);
      }
      return fpr / totalInstances();
    }
docs: Provides the <i>false positive rate</i>. Aka <i>false alarm rate</i>:
  <code>FP / (FP+TN)</code>.
  
  
  @return the false positive rate