docs: def RABC(self):
      """ Return ABC
          轉折點 ABC
      """
      A = self.raw_data[-3]*2 - self.raw_data[-6]
      B = self.raw_data[-2]*2 - self.raw_data[-5]
      C = self.raw_data[-1]*2 - self.raw_data[-4]
      return '(%.2f,%.2f,%.2f)' % (A,B,C)