You can set a repetitive value on the diagonal of an (N \times N) matrix in MATLAB using the diag and repmat functions. Here’s a simple example to help you get started:

% Define the repetitive value and the size of the matrix

value = 5; % The value you want to repeat

N = 10; % Size of the matrix

% Create a vector with the repetitive value

repetitive_vector = repmat(value, 1, N);

% Create the diagonal matrix

A = diag(repetitive_vector);

% Display the matrix

disp(A);

In this example, the matrix A will have the value 5 repeated along its main diagonal. You can adjust the value and N variables to fit your specific needs.

If you have a specific pattern you want to repeat, you can modify the repetitive_vector accordingly. For instance, if you want to repeat a sequence like [1, 2, 3], you can do:

% Define the sequence and the size of the matrix

sequence = [1, 2, 3];

N = 9; % Size of the matrix

% Repeat the sequence to fit the diagonal length

repetitive_vector = repmat(sequence, 1, ceil(N/length(sequence)));

repetitive_vector = repetitive_vector(1:N); % Trim to the correct length

% Create the diagonal matrix

A = diag(repetitive_vector);

% Display the matrix

disp(A);

This will create a matrix with the sequence [1, 2, 3] repeated along the diagonal.