npk {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

    data(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

    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)

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