Why does the one-dimensional variant of a 2-d random walk not work?

There is a two-dimensional random walk that one can find here which works perfectly in Octave. However, when I tried to write a one-dimensional random walk program, I got an error. Here is the program:

t=[];
x=[];
for i=1:100000
    J=rand;
    if J<0.5
        x(i+1)=x(i)+1;
        t(i+1)=t(i)+1;
    else
        x(i+1)=x(i)-1;
        t(i+1)=t(i)+1;
    end
end

plot(t,x)

Here is the error:

error: A(I): index out of bounds; value 1 out of bound 0

Thank you.