Why am I not getting values for my step response transfer function using stepinfo

Using a step response transfer function, I attempted to use stepinfo to gather data on it, but for each value I get NaN or Inf:

ans =

struct with fields:

RiseTime: NaN

SettlingTime: NaN

SettlingMin: NaN

SettlingMax: NaN

Overshoot: NaN

Undershoot: NaN

Peak: Inf

PeakTime: Inf

This is my code:

num=[100, 301, 201];
den=[125, 125, -61, 40];
sys=tf(num,den)
step(sys)
stepinfo(sys)

Answer 1

[Star Strider]

Thjere are two poles in the right-half plane, so the system is unstable —

num=[100, 301, 201];
den=[125, 125, -61, 40];
sys=tf(num,den)

sys =
 
      100 s^2 + 301 s + 201
  -----------------------------
  125 s^3 + 125 s^2 - 61 s + 40
 
Continuous-time transfer function.

figure
pzmap(sys)

Poles = pole(sys)

Poles = 
  -1.4771 + 0.0000i
   0.2385 + 0.3997i
   0.2385 - 0.3997i

Zeros = zero(sys)

Zeros = 2×1

-2.0100 -1.0000

figure
step(sys)
grid

stepinfo(sys)

ans = struct with fields:
         RiseTime: NaN
    TransientTime: NaN
     SettlingTime: NaN
      SettlingMin: NaN
      SettlingMax: NaN
        Overshoot: NaN
       Undershoot: NaN
             Peak: Inf
         PeakTime: Inf

.