Create an equal variance assessment graph of the residuals of a fitted object from the cg package
1 
fit 
A fit object, typically created by the 
trend 
Add a trend line to help assess the trend of the residuals. See
specific method written for the 
cgtheme 
When set to the default 
device 
Can be one of three values:

... 
Additional arguments, depending on the specific method written for the object. See the methodspecific documentation for additional details. 
The graphs plot the square root of the absolute value of the residuals against the fitted value. The notion of using the squared root of the absolute residuals is attributed to John Tukey.
varianceGraph
returns
an invisible NULL
. The main purpose is the side
effect of graphing to the current device.
Contact cg@billpikounis.net for bug reports, questions, concerns, and comments.
Bill Pikounis [aut, cre, cph], John Oleynick [aut], Eva Ye [ctb]
1 2 3 4 5 6 7 8 9 10 11  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")

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