npk                   package:MASS                   R Documentation

Classical N, P, K Factorial Experiment

Description:

     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.

Usage:

     npk

Format:

     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).


Source:

     Imperial College, London, M.Sc. exercise sheet.

References:

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

Examples:

     options(contrasts = c("contr.sum", "contr.poly"))
     npk.aov <- aov(yield ~ block + N*P*K, npk)
     npk.aov
     summary(npk.aov)
     alias(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)

