Assembly of mass Matrix algorithm

I have this code, that generate the "Assembly of mass Matrix algorithm" this code deisgned for (3,3) matrix.

The problem is: how can i upgrade this code for (9*9) matrix.

%% assembly of the mass matrix
function M = MassMar2D(p,t)
clear,clc
p = [0 1 2 2 0;
     0 0 0 1 1];
 t = [1 1 2;
      4 2 3;
      5 4 4]; 
np = size(p,2); % number of nodes
nt = size(t,2); % number of elements
M = sparse(5,5); % allocate mass matrix
for K = 1:nt % loop over elements
    loc2glb = t(1:3,K) % locate to global map
    x = p(1, loc2glb); % node x-coordinates
    y = p(2, loc2glb); %      y
    area = polyarea(x,y); % triangle area
    MK = [2 1 1;
          1 2 1;
          1 1 2]/ 12 * area; % elements mass matrix
    M(loc2glb, loc2glb) = M(loc2glb, loc2glb) ...
        + MK; % add element masses to M
end