Nothing
hovplotBF <- function(x, data, ..., na.rm=TRUE,
main="Brown-Forsyth Homogeneity of Variance",
plotmath=TRUE) {
lPF <- latticeParseFormula(x, data=data)
y <- lPF$left
group <- lPF$right
y.name <- lPF$left.name
group.name <- lPF$right.name
y.median <- tapply(y, group, median, na.rm=na.rm)
y.minus.median <- y - y.median[group]
## panel.hovnew ignores user-specified groups
panel.hovnew <- function(x, y, subscripts, groups, ...) {
panel.abline(h=0, lty=3, col="gray20")
panel.bwplot.superpose(x, y, groups=x,
subscripts=subscripts, ...)
}
A <- bwplot( y ~ group, ..., panel=panel.hovnew)
B <- bwplot( y.minus.median ~ group, ..., panel=panel.hovnew)
C <- bwplot(abs(y.minus.median) ~ group, ..., panel=panel.hovnew)
result <- update(c(y=A,
"y - med(y)"=B,
"abs(y - med(y))"=C,
x.same=TRUE, layout=c(3,1)),
xlab=group.name,
ylab=y.name,
main=main)
if (plotmath)
result <-
update(result,
strip=strip.custom(factor.levels=c(
expression(y),
expression(y-y^scriptstyle(symbol("\136"))),
expression("| "~y-y^scriptstyle(symbol("\136"))~" |"))),
par.strip.text=list(lines=1.5))
result
}
hovBF <- function(x, data=NULL, ..., na.rm=TRUE) {
lPF <- latticeParseFormula(x, data=data)
y <- lPF$left
group <- lPF$right
y.name <- lPF$left.name
group.name <- lPF$right.name
y.median <- tapply(y, group, median, na.rm=na.rm)
y.minus.median <- y - y.median[group]
hov.test <- summary(aov(abs(y.minus.median) ~ group))[[1]]
result <- list(statistic=c(F=hov.test["group","F value"]),
parameters=hov.test[,"Df"],
p.value=hov.test["group","Pr(>F)"],
alternative="variances are not identical",
method="hov: Brown-Forsyth",
data.name=y.name)
names(result$parameters) <- paste("df", sep=":", c(group.name, dimnames(hov.test)[[1]][2]))
class(result) <- "htest"
result
}
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