Step Response: Settling time not showing

When plotting the step response of a system. If I enable the settling time characteristic and it doesn't show, is that implying that the settling time is 0 or that there is no settling time? It also shows NAN when I use stepinfo for the system.

Edit** More Info

So say I use this code to plot the step response of a transfer function:

   s = tf('s');
   G = 645*(1+s)/(0.001*s^3+1.02*s^2+(20*s)+645*(1+s))
   t2 = 0:0.00001:.03; 
   step(G,t2);

Then when I right click the diagram and select characteristics -> settling time, nothing shows up.

Also if I use stepinfo(G)

Settling time only returns NaN

[José-Luis]

Please provide more details. Please do realize that people here have no idea what you are doing.

[Galafried]

Sorry about that I was in a hurry before. I just added more info.

Answer 1

[Star Strider]

This works:

     s = tf('s');
     G = 645*(1+s)/(0.001*s^3+1.02*s^2+(20*s)+645*(1+s))
     t2 = 0:0.00001:.03; 
     [y,t] = step(G,t2);
     si = stepinfo(y,t)

produces:

si = 

          RiseTime: 2.3554e-003
      SettlingTime: 7.3168e-003
       SettlingMin: 875.4812e-003
       SettlingMax: 1.0498e+000
         Overshoot: 7.9921e+000
        Undershoot: 0.0000e+000
              Peak: 1.0498e+000
          PeakTime: 4.9400e-003