generate_a.m

function A = generate_a( N )
    % Generates matrix A
    % N: Integer of size of mesh
    n = N-1;
    meshsize = n*n;

    % Build matrix D
    D_block  = triu(tril(ones(n), 1), -1) - 5*eye(n);
    D_repeat = repmat({D_block}, n, 1);
    D_matrix = blkdiag(D_repeat{:});

    % Setup Identity matrix
    I_vector = ones(meshsize-n, 1)';
    I_lower  = diag(I_vector, n);
    I_upper  = diag(I_vector, -n);

    A = D_matrix + I_lower + I_upper;
end