docs: public static double idf(double totalDocs, double numTimesWordAppearedInADocument) {
          //return totalDocs > 0 ? Math.log10(totalDocs/numTimesWordAppearedInADocument) : 0;
          if (totalDocs == 0)
              return 0;
          double idf = Math.log10(totalDocs / numTimesWordAppearedInADocument);
          return idf;
      }