How can I compile the intermediates of a while loop into a vector

I want to be able to graph the values of all the intermediates, but x is overwritten each time the loop is run. Here's what I have so far.

index = 0; %Counter

while x>1 %continues until x=0

      if mod(x,2)==0; %if even
          x = x/2;
      else %if odd
          x = 3 * x +1;
      end

index = index + 1; %counts how many times for loop runs

end

Answer 1

[Walter Roberson]

After the

index = index + 1

line, add

xlist(index) = x;

then after the loop, xlist will be the list of the x values.