how to convolute 2 signals and generate the pulse train from half cycle sine wave?

clc;
clear all;
close all;
%wt = 0:0.2:pi;
tp=2.2676*10^-3;
Ts=22.67*10^-6;
n=1:Ts:101;
fp=(1/tp);
w=2*pi*fp;
%p=sin(wt);
p=sin(w*n*Ts);
p(find(p<0))=0;
plot(n,p);

data = randi([0,1],1,101);

for k=1:2:100
    if data(k)==0 && data(k+1)==0
        a(k)=1;
    elseif data(k)==0 && data(k+1)==1
        a(k)=i;
    elseif data(k)==1 && data(k+1)==0
        a(k)=-1;
    elseif data(k)==1 && data(k+1)==1 
        a(k)=-i;
        
    end
    
end
y_s=[];
% syms k
y_s=conv(a,p);
plot(n,y_s);

Im trying the convolution but getting error!! can anyone help?
expexted output