What are the ways to sum matrix elements in MATLAB?

Question

Given the matrix:

A = [1 2 3; 4 5 6; 7 8 9];

1. How could you use a for loop to compute the sum of the elements in the matrix?
2. Writ

Answer 1

1)

total = 0;
for i=1:size(A,1)
  for j=1:size(A,2)
    total = total + A(i,j);
  end
end

2)

total = sum(A(:));