% Diagramma l'informazione mutua di un BSC

clear 
close all
figure

alpha=[0:.001:1];
p=[0.45 0.3 0.2 .1 .05 0.0];
I=zeros(length(alpha),length(p));
for i=2:length(alpha)-1,
    for j=1:length(p)
       p1=p(j);
       alpha1=alpha(i);
       Hy=-((1-p1)*alpha1+p1*(1-alpha1))*log2(((1-p1)*alpha1+p1*(1-alpha1)))- ((1-p1)*(1-alpha1)+p1*alpha1)*log2((1-p1)*(1-alpha1)+p1*alpha1);
       if p1==0,
           Hyx=-(1-p1)*log2(1-p1);
       else
           Hyx=-(1-p1)*log2(1-p1)-p1*log2(p1);    
       end
       I(i,j)=Hy-Hyx;
    end
end

for jj=1:length(p)
    I(1,jj)=0;
    I(length(alpha),jj)=0;
end

plot(alpha,I(:,1),'-r','linewidth',1.2);
hold
plot(alpha,I(:,2),'-g','linewidth',1.2);
plot(alpha,I(:,3),'-b','linewidth',1.2);
plot(alpha,I(:,4),'-k','linewidth',1.2);
plot(alpha,I(:,5),'-m','linewidth',1.2);
plot(alpha,I(:,6),'-c','linewidth',1.2);


axis([0 1 0 1.2])
xlabel('Prob(\xi_1)')
ylabel('I(X,Y)    [bit/simbolo]')
grid