plot inverse z transform

I want to plot the sequence described by the inverse transform of the following Pulse Transfer Function

G(z) = (0.6321*z^-1)/(1-1.3679*z^-1+0.3679*z^-2)

writing the code

syms z k
G = (0.6321*z^-1)/(1-1.3679*z^-1+0.3679*z^-2)
g = iztrans(G, z, k)
k = linspace(0,14,15);
stem(g,k)

or even

syms z k
G = (0.6321*z^-1)/(1-1.3679*z^-1+0.3679*z^-2)
g = iztrans(G, z, k)
stem(g)

But there is the following error:

DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use VPA.
Error in
stem(g)

What is the problem?

Answer 1

[Walter Roberson]

stem() does not understand symbolic expressions. You need to evaluate to get numeric expressions.

gn = double( subs(g, sym('k'), k) );
stem(gn, k)

Answer 2

[Priyadharsini B]

syms z

f=z/((z-1)^2)*((z+2)^2)

iztrans(f)