R: Makes a half or full normal plot for the effects from an aov...

qqnorm.aov {gplots} | R Documentation

## Makes a half or full normal plot for the effects from an aov model

### Description

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.

### Usage

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

### Arguments

`y` | A model object inheriting from `aov`
`full` | Full or half normal plot (half is default)
`label` | If `TRUE`, function allows interactive labelling of points in plot, using the mouse
`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

### Details

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.

### Value

If `label=TRUE`, the vector of points identified, else nothing of interest.

### Author(s)

Kjetil Halvorsen kjetil@entelnet.bo

### References

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.

### Examples

    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)

[Package gplots version 3.0.1 Index]