Here's an example M-file:

% Create the mesh [x, y] = meshgrid(linspace(0, Lx, N+1), linspace(0, Ly, N+1));

% Define the problem parameters Lx = 1; Ly = 1; % dimensions of the domain N = 10; % number of elements alpha = 0.1; % thermal diffusivity

% Define the problem parameters L = 1; % length of the domain N = 10; % number of elements f = @(x) sin(pi*x); % source term