How to generate DISCRETE TIME CONVOLUTION in matlabs,

DISCRETE TIME CONVOLUTION  
n0=0:20;
x=5*(-0.5).^n0;
n1=-10:5;
h=(2/3).^n;
n2=-20:10;
y1=conv(x,h);
y=y1(1:length(n2));
subplot(3,1,1);
stem(n0,x);
xlabel('time(sampled)');
ylabel('magnitude x(n)');
title('input signal');
grid on;
subplot(3,1,2);
stem(n1,h);
xlabel('time(sampled)');
ylabel('magnitude h(n)');
title('transfer function h(n)');
grid on;
subplot(3,1,3);
stem(n2,y);
xlabel('time(sampled)');
ylabel('magnitude y(n)');
title('output signal');
grid on;