code: public static double kendallsTau(double[] a, double[] b) {
          return kendallsTau(Vectors.asVector(a), Vectors.asVector(b));
      }
docs: Computes <a href="http://en.wikipedia.org/wiki/Kendall%27s_tau">Kendall's
  tau</a> of the values in the two arrays.  This method uses tau-b, which
  is suitable for arrays with duplicate values.
  
  @throws IllegalArgumentException when the length of the two arrays are
  not the same.