You should always include a link to the old question, so people can look there for context. Of course it is always best to use vectorized code. It is a bad idea to refuse that kind of speed increasing measures. But if you are adamant about not using that other solution, just wrap this code in a for loop if you want to repeat it.
clear variables
clc
==================
N = 10; % number of steps.
M = 10;
for m=1:M
x_t(1) = 0;
for n = 1:N
a = sign(randn);
x_t(n+1) = x_t(n) + a;
end
plot(x_t);hold on
end
xlabel('t'), ylabel('x_t'), title('randomwalk');
