code: def get_MAD(tau):
      
      # tau is ordered so that tau[0] > tau[1] > tau[2]
      for t in tau:
          if isinstance(t, complex):
              return -999
      MAD = math.degrees(numpy.arctan(numpy.sqrt(old_div((tau[1] + tau[2]), tau[0]))) )
      return MAD
docs: input: eigenvalues of PCA matrix
      output: Maximum Angular Deviation