Analysing interactions of fitted models

This vignette presents a brief review about the existing approaches for the post-hoc analysis of interactions in factorial experiments, and describes how to perform some of the cited calculations and tests with the functions of the package phia in R. Those functions include the calculation and plotting of cell means, and testing simple effects, residual effects, and interaction contrasts, among other possibilities. They can be applied to linear and generalized linear models, with or without covariates, and to mixed or multivariate linear models for repeated measures experiments.