A mixed model for investigating a population of asymptotic growth curves using restricted B-splines

  • Geoffrey JonesEmail author
  • Joyce Leung
  • Hugh Robertson


We introduce a new method for modeling a population of growth curves with B-splines, adapting the usual regression spline basis to ensure a horizontal upper asymptote in all fitted curves. The new method is easily implemented in standard statistical software. We motivate and illustrate our method using data on the growth of Brown Kiwi (Apteryx mantelli) in the North Island of New Zealand, including a time-dependent covariate to investigate the effects of different rearing environments on patterns of weight increase.

Key Words

Asymptotic growth Fixed and random effects Functional data analysis Hierarchical model Regression spline 


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Copyright information

© International Biometric Society 2009

Authors and Affiliations

  1. 1.Institute of Information Sciences & TechnologyMassey UniversityPalmerston North
  2. 2.Development and Improvement DivisionDepartment of ConservationWellington

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