# npk

From MASS v7.3-47
by Brian Ripley

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.

- Keywords
- datasets

##### Usage

`npk`

##### Note

This dataset is also contained in R 3.0.2 and later.

##### 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).

##### References

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

##### Examples

`library(MASS)`

```
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)
```

*Documentation reproduced from package MASS, version 7.3-47, License: GPL-2 | GPL-3*

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