Block Diagonal

This code allows you to process block diagonal elements. Its like the generalization of inbuilt diag.

% if size(v,2) == n

% D = diag(v) returns a square diagonal matrix with the block

% (m-by-n) elements of matrix v when on the main diagonal.

% D = diag(v, k) places the (m-by-n) elements of vector v on the kth

% block diagonal. k = 0 represents the main diagonal, k > 0 is above

% the main diagonal, and k<0 is below the main diagonal.

% end

% if size(v,2) > n

% D = diag(v) returns a matrix size(v, 1)-by-n made of block

% (m-by-n) main diagonal elements of matrix v.

% D = diag(v, k) extracts (m-by-n) block elements from matrix v on the

% kth block diagonal. k = 0 represents the main diagonal, k > 0 is above

% the main diagonal, and k<0 is below the main diagonal.

% end

% Note that if v has just 1 column, m = 1, and n = 1, then BlockDiag

% behaves exactly like the inbuilt function Diag.

A = rand(12);
v1 = BlockDiag(A, 2, 2)

v2 = BlockDiag(A, 2, 2, 1)

v3 = BlockDiag(A, 3, 2, -1)

v = rand(12,3);
D1 = BlockDiag(v, 3, 3)

D2 = BlockDiag(v, 3, 3, -1)

D3 = BlockDiag(v, 4, 3, 1)