clear all;
close all;
clc;

%////////////////////////////////////////////////////////////////////////

N = 8;                 % dimension of 2D vector
M = 8;

a(N,M)=0
% //////////////////////////////////////////////////////////////////////

for n=1:M  
    a(1,n)=100;       % setting boundary condition
end
a
dx = 0.139;
dy = 0.139;

%//////////////////////////////////////////////////////////////////////

for t=1:15
    for i=2:(M-1)
        for j=2:(N-1)
    
            a(j,i) = ( ((a(j+1,i)+a(j-1,i)-(2*a(j,i)))/(dx^2)) +  ((a(j,i+1)+a(j,i-1)-(2*a(j,i)))/(dy^2)));
           a(j,i) = (a(j+1,i) + a(j-1,i) + a(j,i+1) + a(j,i-1) )/ (4)
        end
    end
end
a

%/////////////////////////////////////////////////////////////////////////



 [x,y]= meshgrid(0:dx:1,0:dy:1);
 [Ex Ey] = gradient (-a,dx,dy);
 
 
 
 figure(1)
 
contour(x,y,a)
%hold on
figure(2)
quiver (x, y, Ex, Ey)		
%hold off