% voter.m
% each site accepts its neighbor's state with probability p
% 4 neighbors
%                                                           4/3/3           SG

clear all
close all
tic

p = 0.1;
n =100;
T = 10000;
plot_number_of_states = 0;

c = 2;    % number of colors

colormap(gray(c))              % use this with c=2!!!
X=ceil(c*rand(n));              % initial state: random values: 1,2,...,c
image(X)
axis square

for t=1:T

	Z(1,:,:)=X;
	Z(2,:,:)=X(:,[n 1:n-1]);           % states of neighbors left
	Z(3,:,:)=X(:,[2:n 1]);              % states of neighbors right
	Z(4,:,:)=X([n 1:n-1],:);           % states of neighbors above
	Z(5,:,:)=X([2:n 1],:);              % states of neighbors below
	
	Y=rand(n);
	Q=1+ceil(Y.*(Y<p)*4/p);    % Q is 1 with prob.1-p and 2,3,4 or 5 with probability p/4
	
	for i=1:n
        for j=1:n
            X(i,j) = Z(Q(i,j),i,j);         % accept state Q
        end
	end
	
	figure(1)
	image(X)
	
	set(gca,'XTick',[],'YTick',[])
	title(['t = ', num2str(t)])
	axis square
	pause(.001)
    
    if plot_number_of_states
        C(t)=sum(diff(sort(reshape(X,n^2,1)))>0)+1;  % number of different states
    end
    
end

if plot_number_of_states
	figure
	plot(1:length(C),C)
	title('number of different opinions')
	xlabel('time')
end

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