step response of a state space system

[Beginner1]

Hi! 
I am a very beginner in Octave. I need your help in the following task: 
I need to obtain and plot the step response of a system whose state-space
matrices are known and it can be represented by 

xdot=A*x+B*u 
y=C*x+D*u 

For this purpose, I have written this code: 

/%State-space system parameters 
w=314.159; 
ki=1.5; 
kp=5000; 
A=[0 1 0 0 0 0; 0 0 1 0 0 0; 0 -4*w^2 0 0 0 0;0 0 0 0 1 0;0 0 0 0 0 1;0 0 0
0 -4*w^2 0]; 
B=[0 0 0 0 0 0; 0 0 0 0 0 0;0 0 -1 0 1 0;0 0 0 0 0 0;0 0 0 0 0 0;0 0 0 -1 0
1]; 
C=[2*(w^2)*ki  0  ki  0  ki*w  0;0 ki*w 0 2*(w^2)*ki 0 ki]; 
D=[1 0 -kp 0 kp 0;0 1 0 -kp 0 kp]; 

%Perform system simulation 

stname = {'xd1', 'xd2', 'xd3','xq1','xq2','xq3'}; 
sys = ss (A, B,C,D,'stname', stname) 
t=linspace(0,3,1000) 
[y,t,x]=step(sys) 
plot(t,y) 
/

However, an error message is obtained at the console for the command
plot(t,y) saying that the dimensions of one of the plot arrays are not
correct. 

Any suggestion? 

Thanks   



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