1 #!/usr/bin/python

     2 # 11.7

     3 

     4 # N and D polynomials in z^{-1} form; discrete case

     5 import scipy as sp

     6 from l2r import l2r

     7 from scipy import signal

     8 from covar_m import covar_m

     9 

    10 def tfvar(N,dN,D,dD):

    11     N,dN,D,dD = l2r(N,dN,D,dD)

    12     N = N/D[0]

    13     D = D/D[0]

    14     LN, LD = len(N), len(D)

    15     D1 = D

    16     if LD<LN:

    17         D1 = sp.hstack((D, sp.zeros(LN-LD)))

    18         dD1 = dD+LN-LD

    19     H = signal.lti(N, D1)

    20     yvar = covar_m(H,1)

    21     return N,dN,D,dD,yvar