nearest picks the sample closest in time to the indicated one. For example, given the following case fragment:
01 Jun 03 20 Jun 03 30 Jun 03 15 Oct 03 02 Nov 03 HDL 2.0 2.1 2.2 2.4 pending LDL 4.5 4.7 4.8 3.1 Trig 3.2 3.8 3.6 3.5 LipidDrug N Y / Y
nearest Trig to first LDL is 3.8
nearest LDL to max Trig is 4.7