code: def fit_power(xs, ys)
        a, b, rr = fit(xs, ys, tran_x: ->(x) { Math.log(x) },
                               tran_y: ->(y) { Math.log(y) })
  
        [a, Math.exp(b), rr]
      end
docs: Finds a line of best fit that approxmimates power function
  
   Function form: y = bx^a
  
   @return [Numeric, Numeric, Numeric]
     returns a, b, and rr values
  
   @api public