Hi Andee,
It would be very nice to be able to combine categories using a graph. (TinkerPlots gives you a way of doing this.) I’ll add it as a feature request.
You don’t have to write a formula, though. As shown in the screen capture, you can use the case table to group by the attribute that has the categories you want to combine. Create a new attribute in which you copy the existing category names, except where you want to combine.
Hope that helps!
Bill
