clc
clear
num=[0 1 -0.3 -0.06 0.008]; %  分子  Z^-1降冪排列
den=[1 -0.5 -0.49 0.125 0.06];%  分母 Z^-1降冪排列
H=filt(num,den)%Transfer function: 
%( z^-1 - 0.3 z^-2 - 0.06 z^-3 + 0.008 z^-4)/(1 - 0.5 z^-1 - 0.49 z^-2 + 0.125 z^-3 + 0.06 z^-4)

sys=ss(H); %  Creates state-space model or converts model to state space.
%sys1=sys(1)
%sys=ss(sys)
[A B C D]=tf2ss(num,den) % calculates the state-space  representation:
ito=obsv(A,C); %Compute the observability matrix.
to=inv(ito);
ao=ito*A*to
bo=ito*B
co=C*to
sys=ss(ao,bo,co,D)