p=0.5;
n=100;
t=1:n;
y=rand(1,n);
figure
x=-(y<=0.5)+(y>0.5);
plot(x,'o')
axis([0,100,-2,2])
p=0.6;
x=-(y<=p)+(y>p);
figure
plot(x,'o')
axis([0,100,-2,2])

%nahodna prochazka
x=x'*ones(1,n);
xt=triu(x);
S=sum(xt);
figure
plot(S)

p=0.5;
x=-(y<=p)+(y>p);
S=sum(triu(x'*ones(1,n)));
figure
plot(S)