def fit_logarithmic(xs, ys)
      fit(xs, ys, tran_x: ->(x) { Math.log(x) })
    end
def fit_logarithmic(xs, ys)
      fit(xs, ys, tran_x: ->(x) { Math.log(x) })
    end
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