How to plot state space variables against time on unit step input?
Looks like matlab step function can already do that 

I have solved it using the following equations:

[y,t,x] = step(ss_model,1) % X here will have trajectories for the 
x1 = [ 1 0 0 0]*x';
x2 = [ 0 1 0 0]*x';
x3 = [ 0 0 1 0]*x';
x4 = [ 0 0 0 1]*x';