We have a frequent requirement to translate numeric ranges into banded value categories. If the bands are linearly spaced then this can be done easily using aggregations and histogram ranges, unfortunately if the bands are non linear (i.e 0 or belas one category, linear to an upper limit, then greater than the upper limit) it becomes tricky.
This can be solved inelegantly with a formula field and a lot of nested if functions. It would be useful to have some form of case statement/function that would make this more elegant.
You should be able to do this using a single IF statement. In Omniscope 2.5 we extended IF to support multiple decisions. See:
http://www.visokio.com/functions-guide#IF