Merging categories in a polynomial
I am working with a dataset that involves aviation data which is reported by phase of flight. I sometimes need to convert a dozen possible phases of flight into only 2, climbing and descending. How do I look at the phase of flight, compare it to a list that shows which are climbing and which are descending and then create a new attribute that is binomial and either climbing or descending? I know there has to be an operator that will do this but I am striking out in finding it.