Here are a few corrections you can make in your code:
- The size of vector x should be
, i.e. 
not 
. - Matrix "H" and variable "k" need to be defined appropriately.
- No need to use "i" as a symbolic variable, it can function perfectly fine as a loop variable.
- Indexing used in the loop is incorrect and needs to be fixed.
- The sum can be directly computed numerically using a loop and "symsum" is not needed for the same.
x = [1; 2; 3; 4];
total_size = size(x, 1);
N = total_size/2;
% Initialize output matrix
H = zeros(N, N);
% Compute matrix H
for i = 1:N
for j = 1:N
% Calculate the sum for each element
sum_val = 0;
for k = 1:N
% Ensure we don't exceed vector bounds
if (k + j - 1) <= total_size
sum_val = sum_val + x(k) * x(k + j - 1);
end
end
H(i, j) = sum_val;
end
end
disp(H);
