MATLAB - subs method doesn't work on symbolic vector of indexed variables

Question

Consider the following code:

A = sym('a', [1, 2]);
b = sym('b');
ans = A.^2 + b;
A = [1, 2];
b = 4;
subs(ans)

This yields the output

ans = [ a1^2 + 4, a2^2 + 4]

Whereas I would have wanted it to produce

ans = [ 5, 8]

What is required for the vector to be converted to numeric values aswell?

Answer 1

Here's a simpler solution:

syms A b;        %Initializing symbolic variables
expr = A^2 + b;  %Your expression (element-wise square is taken by default for sym class) 

A = [1 2];   b=4;  %Assigning the values
subs(expr)         %Substituting symbolic variables with corresponding assigned values  

Output as desired:

ans = 
[ 5, 8]

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Comments:

1. Always avoid dynamic variables. In your code, you're specifying A to be [1, 2] but your expression doesn't actually have A in it. It has a1 and a2 (and b obviously).
2. Don't name your variables/functions after the reserved variable names or in-built functions. ans is used for the Most Recent Answer when expressions are not assigned to anything else. (That's why I replaced ans in your code with expr)