title: The analysis of longitudinal data using mixed model L-splines.
abstract: L-splines are a large family of smoothing splines defined in terms of a linear differential operator. This article develops L-splines within the context of linear mixed models and uses the resulting mixed model L-spline to analyze longitudinal data from a grassland experiment. In the spirit of time-series analysis, a periodic mixed model L-spline is developed, which partitions data into a smooth periodic component plus smooth long-term trend.
authors.affiliation: Rothamsted Research, Harpenden AL5 2JQ, UK. sue.welham@bbsrc.ac.uk
authors.forename: Sue J
authors.initials: SJ
authors.lastname: Welham
authors.forename: Brian R
authors.initials: BR
authors.lastname: Cullis
authors.forename: Michael G
authors.initials: MG
authors.lastname: Kenward
authors.forename: Robin
authors.initials: R
authors.lastname: Thompson
mesh_terms: D018533:Biomass; D001699:Biometry; D003627:Data Interpretation, Statistical; D016013:Likelihood Functions; D016014:Linear Models; D008137:Longitudinal Studies; D008954:Models, Biological; D015233:Models, Statistical; D006109:Poaceae