Simple incorporation of interactions into additive models

Biometrics. 2001 Jun;57(2):539-45. doi: 10.1111/j.0006-341x.2001.00539.x.


Often, the functional form of covariate effects in an additive model varies across groups defined by levels of a categorical variable. This structure represents a factor-by-curve interaction. This article presents penalized spline models that incorporate factor-by-curve interactions into additive models. A mixed model formulation for penalized splines allows for straightforward model fitting and smoothing parameter selection. We illustrate the proposed model by applying it to pollen ragweed data in which seasonal trends vary by year.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Biometry / methods
  • Cycadopsida
  • Michigan
  • Models, Statistical*
  • Plant Proteins*
  • Pollen*
  • Rain
  • Seasons


  • Plant Proteins