% CANALE DISCRETE -> doar Canalul binar simetric
% Lucrare laborator TTI
% Serban OPRISESCU, 19 Oct 2010

%Introducere valori:
prompt={'p(x1)=',...
        'p='};
name='Introduceti valorile';
numlines=1;
defaultanswer={'0.946','0.789'};
answer=inputdlg(prompt,name,numlines,defaultanswer);
px1=str2num(cell2mat(answer(1)));  
p=str2num(cell2mat(answer(2)));

% De aici incep calculele:
px2=1-px1; % p(x2)

py1=px1*(1-p)+px2*p;  % p(y1)
py2=px2*(1-p)+px1*p;  % p(y2)

disp('    p(y1)     p(y2)');
disp([py1  py2]);

HX=-px1*log2(px1)-px2*log2(px2); % H(X)
HY=-py1*log2(py1)-py2*log2(py2); % H(Y)

HYcX = -(p*log2(p)+(1-p)*log2(1-p));  % H(Y|X)
HXvY = HX+HYcX; % H(X,Y)
HXcY = HXvY-HY; % H(X|Y)

I = HX + HY - HXvY; % transinformatia
C = 1 + p*log2(p)+(1-p)*log2(1-p); % capacitatea canalului

disp('     p(x1)     p        H(X)      H(Y)       H(X,Y)    H(X|Y)    H(Y|X)   I(X,Y)   C');
disp([px1  p  HX  HY  HXvY  HXcY  HYcX  I   C]);

%Grafic C: 
pgr=0:0.01:1;
Cgr=1 + pgr.*log2(pgr)+(1-pgr).*log2(1-pgr);
figure,plot(pgr,Cgr), text(p,C,['* C=',num2str(C)]);