code: def fit_logarithmic(xs, ys)
        fit(xs, ys, tran_x: ->(x) { Math.log(x) })
      end
docs: Find a line of best fit that approximates logarithmic function
  
   Model form: y = a*lnx + b
  
   @param [Array[Numeric]] xs
     the data points along X axis
  
   @param [Array[Numeric]] ys
     the data points along Y axis
  
   @return [Numeric, Numeric, Numeric]
     returns a, b, and rr values
  
   @api public