code: function linreg(values_x, values_y) {
      var sum_x = 0;
      var sum_y = 0;
      var sum_xy = 0;
      var sum_xx = 0;
      var count = 0;
  
      /*
       * We'll use those variables for faster read/write access.
       */
      var x = 0;
      var y = 0;
      var values_length = values_x.length;
  
      if (values_length != values_y.length) {
          throw new Error('The parameters values_x and values_y need to have same size!');
      }
  
      /*
       * Nothing to do.
       */
      if (values_length === 0) {
          return [ [], [] ];
      }
  
      /*
       * Calculate the sum for each of the parts necessary.
       */
      for (var v = 0; v < values_length; v++) {
          x = values_x[v];
          y = values_y[v];
          sum_x += x;
          sum_y += y;
          sum_xx += x*x;
          sum_xy += x*y;
          count++;
      }
  
      /*
       * Calculate m and b for the formular:
       * y = x * m + b
       */
      var m = (count*sum_xy - sum_x*sum_y) / (count*sum_xx - sum_x*sum_x);
      var b = (sum_y/count) - (m*sum_x)/count;
  
      return [m, b];
  }
docs: /*
  Least squares linear regression fitting.