code: public static int scott(double[] x) {
          double h = Math.ceil(3.5 * Math.sd(x) / Math.pow(x.length, 1.0/3));
          return bins(x, h);
      }
docs: Returns the number of bins by Scott's rule h = 3.5 * &sigma; / (n<sup>1/3</sup>).
  @param x the data set.
  @return the number of bins