Analysis of Two-Way Tables a la Tukey

Version: 0.7.0

The twoway package provides analysis and graphical methods for two-way tables with one observation per cell, most typically used in an Analysis of Variance (ANOVA) context. The methods follow Tukey (1949), “One Degree of Freedom for Non-additivity”, explained more concretely in Tukey (1972), Exploratory Data Analysis, but the graphical ideas are more interesting and general:

• How to display an assumed additive relation between two factors graphically, and visualize departures from an additive fit? The plot method here uses a rectangle for the row and column effects, but rotated 40 degrees so that the vertical axis represents the fitted value under an additive model. In this, the actual value can be shown as a vertical segment representing the departure from an additive model.

• How to assess visually whether a power transformation of the response,