Matalb code to verify delta modulation

Code:

clc

clear all;

t=0:1/29:1;

f=1;

x=4*sin(2*pi*f*t);

x=[x ones(1,10) x];

y= zeros(1,length(X));

d= zeros(1,length(X));

e = zeros (1,length(x));

s=0.1;

for i=5: length(x)

if(x(i)-y(i-1))>=0

y(i)=x(i) +s;

   d(i) = -1;

end

if(sum(d(i-4:i)))>3

  s=s+0.01;

elseif(sum(d(i-4:i)))<-3

s=s+0.01;

else

s=s;

end

pause;

figure; plot(x);hold on;

stem(y,'m');e=x-y;plot(e,'r');

title('input,tracking and error graph');

subplot 212; stem (d,'k');title('output data signal')

end

Output: