Trying to plot a step response of a given transfer function.

First time posting here so am not sure how exactly to format this or ask this. Simply I am trying to plot the step response of a given transfer function but I keep getting an error stating

"Error using DynamicSystem/step (line 95)

Cannot simulate the time response of improper (non-causal) models.

Error in Lab_1_JGerman (line 99)

[Y, t]=step(sys,10,OPT);"

Here is my code.

m1=1;
m2=1;
c1=1;
c2=1;
k01=0;
k12=100;
k23=10;

s = tf('s')

p1 = [m1*s^2+c1*s+(k01+k12)];
p2 = [m2*s^2+c2*s+(k12+k23)];
p21 = p2/(p1*p2 - k12*k12);

tf1=p2;
sys=tf1;

OPT = stepDataOptions('StepAmplitude', 100);
[Y, t]=step(sys,10,OPT);

plot(t,Y,'r')
hold on 
title ('Step Response')
xlabel ('Time (S)')
ylabel("Amplitude)")
grid on

Answer 1

[Fangjun Jiang]

You probably meant tf1=p21. p2 itself is improper. I assume you know what it means in control theory.

[Jorje German]

OMG You are so right. I completly missed it. Yes p2 would not make sense at all. Thank you. Been staring at it for 10 minutes now for a typo.