category composed of multiple simpler categories

let's say I have a categorical array containing {a,b,c,a+c,a+b,...} and so on. one can see that only three categories exist whcih are {a,b,c}, but when I convert the array containing strings indicating the existing categories, each element of the set {a+c,a+b,c+b,...} becomes a category itself. I can solve this by building a function that returns the existing (simple,basic) categories, but I think this can be solved by a built function the operates on catergorical arrays directly.

Any advice?

[dpb]

Either the combinations are also categories or they aren't...if they aren't really categories when combined, then don't convert them to categorical but use grouping variables and/or set functions for the combinations.

It's not completely clear what the objective/need is from the description, but there's not a "compound category" categorical variable class.

If you have a specification for what this needs be, I suppose you could create one.

[Mahmoud Elbeltagy]

Thank you!, the purpose of my question was to see of there is a way to deal with this situation while the variable class is categorical.

[dpb]

Well, it's not at all clear what "deal with this situation" means.