In the expression A[\,k], k can be a vector as well. For example, if A is , A[\, 1:n-1] would return the elements of the upper triangular part of A (as a vector).
>> A = [1, 2, 3; 4, 5, 6; 7, 8, 9] 1 2 3 4 5 6 7 8 9 >> A[\, 1:2] 2 6 3 >> A[1,1:2] = 0 1 0 0 4 5 0 7 8 9If A and B are two matrices, A[\, 1:9]=B[\,1:9] would copy the upper triangle of B to A.