MATLAB Programming

Operating on Diagonal Matrices
17 24 1 8 15
23 5 7 14 16
4 6 13 20 22
10 12 19 21 3
11 18 25 2 9
diag(A, 2)
ans =
1
14
22
% Return contents of second diagonal of A
Returning a Triangular Portion of a Matrix
The tril and triu functions return a triangular portion of a matrix, the
former returning the piece from the lower left and the latter from the upper
right. By default, the main diagonal of the matrix divides these two segments.
You can use an alternate diagonal by specifying an offset from the main
diagonal as a second input argument:
A = magic(6);
B = tril(A, -1)
B =
0 0 0 0 0 0
3 0 0 0 0 0
31 9 0 0 0 0
8 28 33 0 0 0
30 5 34 12 0 0
4 36 29 13 18 0
Concatenating Matrices Diagonally
You can diagonally concatenate matrices to form a composite matrix using the
blkdiag function. See “Creating a Block Diagonal Matrix” on page 1-10 for
more information on how this works.
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