A classical N, P, K (nitrogen, phosphate, potassium) factorial experiment on the growth of peas conducted on 6 blocks. Each half of a fractional factorial design confounding the NPK interaction was used on 3 of the plots.

`npk`

The `npk`

data frame has 24 rows and 5 columns:

`block`

which block (label 1 to 6).

`N`

indicator (0/1) for the application of nitrogen.

`P`

indicator (0/1) for the application of phosphate.

`K`

indicator (0/1) for the application of potassium.

`yield`

Yield of peas, in pounds/plot (the plots were (1/70) acre).

Venables, W. N. and Ripley, B. D. (2002)
*Modern Applied Statistics with S.* Fourth edition. Springer.

# NOT RUN { options(contrasts = c("contr.sum", "contr.poly")) npk.aov <- aov(yield ~ block + N*P*K, npk) npk.aov summary(npk.aov) coef(npk.aov) options(contrasts = c("contr.treatment", "contr.poly")) npk.aov1 <- aov(yield ~ block + N + K, data = npk) summary.lm(npk.aov1) se.contrast(npk.aov1, list(N=="0", N=="1"), data = npk) model.tables(npk.aov1, type = "means", se = TRUE) # }