Diagonal of non-square matrix

How can I build this matrix? All elements are zero except those three main diagonals. n is any given number.

Answer 1

[Matt J]

n=8;
R=[2,3,4,zeros(1,n+2-3)];
C=[2,zeros(1,n-1)];

T=toeplitz(C,R)

T = 8×10

2 3 4 0 0 0 0 0 0 0 0 2 3 4 0 0 0 0 0 0 0 0 2 3 4 0 0 0 0 0 0 0 0 2 3 4 0 0 0 0 0 0 0 0 2 3 4 0 0 0 0 0 0 0 0 2 3 4 0 0 0 0 0 0 0 0 2 3 4 0 0 0 0 0 0 0 0 2 3 4

[Shuqing Qi]

Thank you!

Answer 2

[Bruno Luong]

n = 8;
A = spdiags([2 3 4]+zeros(n,1),0:2,n,n+2);
A = full(A) % if prefered

A = 8×10

2 3 4 0 0 0 0 0 0 0 0 2 3 4 0 0 0 0 0 0 0 0 2 3 4 0 0 0 0 0 0 0 0 2 3 4 0 0 0 0 0 0 0 0 2 3 4 0 0 0 0 0 0 0 0 2 3 4 0 0 0 0 0 0 0 0 2 3 4 0 0 0 0 0 0 0 0 2 3 4

[Shuqing Qi]

Thank you!

Answer 3

[Clayton Gotberg]

n = 5; % Example input
diagonals = [2 3 4];

% Method 1:
matrix = zeros(n,n+2); % Preallocate for speed
extra_zeros = zeros(1,n-1); 
matrix_row = [diagonals extra_zeros];

for k = 1:n
    matrix(k,:) = matrix_row;
    matrix_row = circshift(matrix_row,1);
end

% Method 2:
diagonal_one = [diag(repmat(diagonals(1),n,1)) zeros(n,2)];
diagonal_two = [zeros(n,1) diag(repmat(diagonals(2),n,1)) zeros(n,1)];
diagonal_three = [zeros(n,2) diag(repmat(diagonals(3),n,1))];

matrix = diagonal_one+diagonal_two+diagonal_three;

The second method is a little faster.

[Shuqing Qi]

Thank you!