k=1;
num=[2*k,k];
den=conv([1,0,0],conv([.25,1],[.25,1]));
[A,B,C,D]=tf2ss(num,den);
x0=[0,0,0,0];
v=1;
t0=0;
tf=10;
h=0.25;
r=1;
[t,y]=ode4(A,B,C,D,x0,h,r,v,t0,tf)；
plot(t,y),grid