%try cosine wave plot also
%a=.5;  
pi=3.14;
f=1;

x=[0 0 0 1 1 0 1 1 0 0 1 0  1 1 0 1];
nx=size(x,2);

i=1;
while i<nx+1
    t = i:0.001:i+2;
    if x(i)==0 && x(i+1)==0
        z=sin(2*pi*f*t-3*pi/4);
        dibit=0;
    elseif x(i)==0 && x(i+1)==1
        z=sin(2*pi*f*t-pi/4);
        dibit=1;
    elseif x(i)==1 && x(i+1)==0
        z=sin(2*pi*f*t+pi/4);
        dibit=2;
    else
        z=sin(2*pi*f*t+3*pi/4);
        dibit=3;
    end
    %subplot(2,1,1);
    plot(t,dibit,'r');
    %grid on;
    hold on;
    %subplot(2,1,2);
    plot(t,z);
    hold on;
    grid on;
    axis([1 20 -3 3]);
    i=i+2;