cg (version 0.9-5)

varianceGraph: Variance Graphs

Description

Create an equal variance assessment graph of the residuals of a fitted object from the cg package

Usage

varianceGraph(fit, trend = NULL, cgtheme = TRUE,
 device = "single", ...)

Arguments

fit

A fit object, typically created by the fit generic function.

trend

Add a trend line to help assess the trend of the residuals. See specific method written for the fit argument.

cgtheme

When set to the default TRUE, ensures a trellis device is active with limited color scheme. Namely background, strip.shingle, and strip.background are each set to "white".

device

Can be one of three values: [object Object],[object Object],[object Object]

...

Additional arguments, depending on the specific method written for the object. See the method-specific documentation for additional details.

Value

• varianceGraph returns an invisible NULL. The main purpose, of course, is the side effect of graphing to the current device.

concept

• equal variance
• residual diagnostics

Details

The graphs plot the square root of the absolute value of the residuals against the fitted value.

See Also

varianceGraph.cgOneFactorFit

Examples

data(canine)
canine.data <- prepareCGOneFactorData(canine, format="groupcolumns",
                                      analysisname="Canine",
                                      endptname="Prostate Volume",
                                      endptunits=expression(plain(cm)^3),
                                      digits=1, logscale=TRUE, refgrp="CC")
canine.fit <- fit(canine.data)

varianceGraph(canine.fit)

varianceGraph(canine.fit, model="olsonly")