qqnorm.aov | R Documentation |

Makes a half or full normal plot for the effects from a model
inheriting from
class `aov`

. One can interactively label the points in the plot.

## S3 method for class 'aov' qqnorm(y, full=FALSE, label=FALSE, omit=NULL, xlab=paste(if (full) "" else "Half", " Normal plot"), ylab="Effects", ...)

`y` |
A model object inheriting from |

`full` |
Full or half normal plot (half is default) |

`label` |
If |

`omit` |
Numeric or character vector of effects to omit, the intercept is always omitted |

`xlab` |
Horizontal axix label |

`ylab` |
Vertical axis label |

`...` |
Further arguments to be given to the plot function |

Produces a (half) normal plot of the effects from an AOV model. The idea behind the plot is that most effects will be small or null, and this effects can be used as a basis for estimation of the experimental variance. This small effects will show up in the plot as a straight line, other effects can be judged against this as a background. Heavily used by Box, Hunter \& Hunter, which attributes the idea to Daniel.

This is a simpler implementation than the one in S-Plus.

If `label=TRUE`

, the vector of points identified, else nothing of
interest.

Kjetil Halvorsen kjetil@entelnet.bo

Box, Hunter and Hunter: Statistics for Experimenters. An Introduction
to Design, Data Analysis and Model Building. Wiley.

Daniel, C (1976): Applications of Statistics to Industrial
Experimentation. Wiley.

Daniel, C (1959): Use of half-normal plot in interpreting factorial
two-level experiments. *Technometrics.***1**, 149.

library(MASS) data(npk) npk.aov <- aov(yield ~ block + N*P*K, npk) qqnorm(npk.aov) ## interactive labeling of points. Click mouse on points to show label. if (dev.interactive()) qqnorm(npk.aov, omit=2:6, label=TRUE)

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