code: function root_mean_square(x) {
          if (x.length === 0) return null;
  
          var sum_of_squares = 0;
          for (var i = 0; i < x.length; i++) {
              sum_of_squares += Math.pow(x[i], 2);
          }
  
          return Math.sqrt(sum_of_squares / x.length);
      }
docs: root mean square (RMS)  a mean function used as a measure of the magnitude of a set of numbers, regardless of their sign  this is the square root of the mean of the squares of the input numbers  This runs on `O(n)`, linear time in respect to the array