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