transfer function, z^-1 form

[David PICARD]

I need some help to define the following transfer function :

  0.381417 z^-1 + 0.310306 z^-2
---------------------------------
1 - 0.857089 z^-1 + 0.548812 z^-2

This is a 2nd order system : w0=1, Damp=1.3, Gain=1.0, Te=1s

I tried :
-->z=%z;
-->sys=syslin(1.0,(0.38*z^-1+0.31*z^-2)/(1+0.86*z^-1+0.55*z^-2))
sys  =

      0.31 + 0.38z
    ----------------
                    2
    0.55 + 0.86z + z


But it NOT what I asked !!! Help !

It is so straightforward with GNU Octave, that I am really frustrated !
> sys=tf([0.000000 0.381417 0.310306],[1.000000 -0.857089 0.548812],1.0);
> step(sys)   // shows the oscillating, stabilizing step response