PARTIAL MATRIX TECHNIQUES

摘要: Partical matrix techniques are those in which gravity models fitted to a partially observed of trips and journey costs, used infer the unobserved cells. This paper reviews theoretical basis from such have been developed, demonstrates need pay careful attention underlying assumptions, effect require that model be good fit data (and also "fit" data). Circumstances described estimates for cells may not uniquely determined, effects structure on reliability (assuming these unique) discussed. Ways suggested further empirical research might demonstrate whether given pattern observations would lead particularly error-prone estimates. (a) (TRRL)