How do I get an Expression to Use the Value of a Variable that was Assigned after the Expression was Defined?

Suppose I assign to a sym as follows:

syms z f g

Define f in terms of z

f = 2*z

f = 

Now assign a value to z

z = sym(2)*1i;

But f is still expressed in terms of z and it doesn't seem to substitute the value for z

f

f = 

simplify(f)

ans = 

simplify(f - sym(2)*1i)

ans = 

But assigning to a new expression in terms of z works as expected.

g = 2*z

g = 

How do I get the SMT to realize that f = 2i?

Answer 1

[Steven Lord]

Use subs.

syms z
f = 2*z

f = 

z = 4;
f

f = 

g = subs(f)

g = 

8