Use for loop index to access the vector as below
%if true
% code
% end
>> r=exprnd(1/8, 1,5);
>> at=cumsum(r);
>> st=exprnd(1/8, 1, 5);
>> n = 0;
>> ord=2:1:6;
>> n=0;
>> for x=1:5; %x defines # of sims
if at(ord(x)-1) + cumsum(st(ord(x)-1)) ==at(ord(x))
n=n
elseif at(ord(x)-1) + cumsum(st(ord(x)-1)) < at(ord(x))
n=n-1
else
n=n+1
plot(n)
end
end
