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.
1 
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).
Imperial College, London, M.Sc. exercise sheet.
Venables, W. N. and Ripley, B. D. (2002) Modern Applied Statistics with S. Fourth edition. Springer.
1 2 3 4 5 6 7 8 9 10  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)

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