inverce laplace and ploting data

I need to verify this figure by obtaining poles and c(t) from G(s) and plotting unit step response for each case. But I couldn't go to the inverse laplace. where am i doing wrong ?

s = zpk('s')
Gs=(9)/(s^2+9*s+9);
pole(Gs)
zero(Gs)
Ct=ilaplace(Gs)
figure
plot(Ct)

[Rena Berman]

(Answers Dev) Restored edit

[Star Strider]

Thank you.

Answer 1

[Star Strider]

I believe that what you actually want is:

s = zpk('s')
Gs=(9)/(s^2+9*s+9);
pole(Gs)
zero(Gs)
% Ct=ilaplace(Gs)
figure
step(Gs)

since under other circumstances (specifically using the Symbolic Math Toolbox), plotting ilaplace of a symbolic transfer function (using fplot) would return the impulse response. To plot a symbolic step response, you would divide ‘Gs’ by ‘s’, then use fplot.