%NRZ polar
b=[1 0 1 0];
%bits to level mapping

for p=1:length(b)
    if b(p)==1;
        x(p)=5;

    else
        x(p)=0;

    end
end

i=1;

t= 0:0.01:length(b);
for j=1:length(t)
if t(j)<=i

    y(j)=x(i)

else
    i=i+1;

   y(j)=x(i);
end
end

plot(t,y,'b');
axis ([ 0 7 -2 7]);
xlabel('time');
ylabel('ampitude');