if…else chooses between two tests, based on some true/false conditional value. For example, given the following case fragment:
13 Feb 03 03 Oct 03 16 Nov 03 20 Dec 03 ABC 2.5 3.2 2.9 2.7 GHF 3.4 3.6 3.3 3.1 Sex F
max (GHF if Sex is “F” else ABC) > 3.5