Treemap multiple values in one column

Hi all,

I want to make a treemap, but I have sometimes multiple values in one column (which is correct). For example, if I only had 5 oberservations, it could look like this:

Value a

Value b

Value a and b

Value a

Value a

Currently i am seeying 3 values in my treemap: a, b, and a & b, but i want to structure it in such way that you can see how often a or be is mentioned. So in the treemap value a should represent 4 and b should represent 2. How do I make this work?