previous to

previous…to… picks the latest non-blank value prior 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                       3.1
Trig          3.2                                    3.6
LipidDrug     N                         Y            /

previous HDL to max LDL is 2.1

previous HDL to most recent Trig is 2.2

previous HDL to first LDL is 2.0