Sampling by Reversing The Landmarking Process

Variations of the commonly applied landmark sampling are presented. These samplings are "forward" landmarking such that each stack of data is created by first selecting landmarks and then including the subsequent observations of the selected landmarks. Unlike these forward landmarking samplings, a "backward" or "reverse" landmarking is proposed with a flexible "progressive" weighting on selecting different types of events and non-events. The backward landmark sample is compared with those forward landmark samples with a real world mortgage data. Results show that the backward landmark sample has smaller sampling errors than of those forward landmark samples.