Nothing

```
##
## p3d:cell.R
## 2011-12-22
##
## Last modified: 6-14-2009 by Michael Friendly
# - combined cell.R, cell.default, cell.glh into a single file
# - renamed first argument to 'object' for consistency as S3 methods
## TODO: Since the ellipses aren't plotted directly, it's not clear why arguments such as
# las, lwd, lty, etc. are needed here. These would normally be used only if the add
# argument was implemented in the code for cell.default.
cell <-
function(object, ... ) {
UseMethod("cell")
help <- "
See help for car::confidence.ellipse.lm
except that 'cell' returns the points to form the ellipse
which must be plotted with plot(...,type='l') or lines(...)
-- Use dfn to determine Sheffe dimension, i.e. dfn = 1 to generate ordinary CIs, dfn = 2 for 2-dim CE, etc.
-- TODO: extend to 3 dimensions if which.coef has length 3
"
}
cell.default <-
function (object, which.coef, levels = 0.95, Scheffe = FALSE, dfn = 2,
center.pch = 19, center.cex = 1.5, segments = 51, xlab, ylab,
las = par("las"), col = palette()[2], lwd = 2, lty = 1,
add = FALSE, ...)
{
which.coef <- if (length(coefficients(object)) == 2)
c(1, 2)
else {
if (missing(which.coef)) {
if (any(names(coefficients(object)) == "(Intercept)"))
c(2, 3)
else c(1, 2)
}
else which.coef
}
coef <- coefficients(object)[which.coef]
xlab <- if (missing(xlab))
paste(names(coef)[1], "coefficient")
ylab <- if (missing(ylab))
paste(names(coef)[2], "coefficient")
if(missing(dfn)) {
## FIXME: df.terms below is considered a global (undefined) object
if (Scheffe) dfn <- sum(df.terms(object))
else 2
}
dfd <- df.residual(object)
shape <- vcov(object)[which.coef, which.coef]
ret <- numeric(0)
ret <- ell( coef, shape, sqrt(dfn * qf(levels, dfn, dfd)))
colnames(ret) <- c(xlab, ylab)
ret
}
cell.glh <-
function (object, which.coef = 1:2, levels = 0.95, Scheffe = FALSE, dfn = 2,
center.pch = 19, center.cex = 1.5, segments = 51, xlab, ylab,
las = par("las"), col = palette()[2], lwd = 2, lty = 1,
add = FALSE, ...)
{
# BUGS: works only on first element of glh list
# glh should be restructured to have two classes: waldList and wald
obj <- object[[1]]
coef <- obj$coef[which.coef]
xlab <- if (missing(xlab))
paste(names(coef)[1], "coefficient")
ylab <- if (missing(ylab))
paste(names(coef)[2], "coefficient")
dfd <- obj$anova$denDF
shape <- obj$vcov[which.coef, which.coef]
ret <- ell( coef, shape , sqrt( dfn * qf( levels, dfn, dfd)))
colnames(ret) <- c(xlab, ylab)
ret
}
```

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