Tidsskriftspublikasjon » Vitenskapelig artikkel
The importance of functional marginality in model building - A case study
Chemometrics and Intelligent Laboratory Systems ; Volume 87. p. 98–106. 2007
Cederkvist, Henrik René; Aastveit, Are Halvor; Næs, Tormod
Polynomial regression models are often used in cases where non-linearity is present between regressors and response. Functional marginality puts certain constraints on polynomial models in tenus of which regressors that need to be present; for example, if the interaction term x(1)x(2) is in the model both x(1) and x(2) need to be present. This paper focuses on variable selection procedures, which are constrained by functional marginality and how functional marginality affects prediction ability of the models using least squares (LS) regression and partial least squares (PLS) regression. A new variable selection procedure for PLS is presented. Detailed computations are performed on three different data sets. The main conclusion obtained is that the restriction of functional marginality either gives similar results to the unrestricted results or it improves them. (C) 2006 Published by Elsevier B.V.