# mark.H0: Mark a point null hypothesis in an HE plot

## Description

A utility function to draw and label a point in a 2D (or 3D) HE plot
corresponding to a point null hypothesis being tested.
This is most useful for repeated measure designs where null
hypotheses for within-S effects often correspond to (0,0).

## Usage

mark.H0(x = 0, y = 0, z=NULL, label, cex = 2, pch = 19, col = "green3", lty = 2, pos = 2)

## Arguments

x

Horizontal coordinate for H0

y

Vertical coordinate for H0

z

z coordinate for H0. If not NULL, the function assumes that
a `heplot3d`

plot has been drawn.

label

Text used to label the point. Defaults to `expression(H[0])`

in 2D plots.

cex

Point and text size. For 3D plots, the function uses
`size=5*cex`

in a call to `points3d`

.

pch

Plot character. Ignored for 3D plots.

col

Color for text, character and lines

lty

Line type for vertical and horizontal reference lines. Not
drawn if `lty`

=0.

pos

Position of text. Ignored for 3D plots

## Value

None. Used for side effect of drawing on the current plot.

## Examples

# NOT RUN {
Vocab.mod <- lm(cbind(grade8,grade9,grade10,grade11) ~ 1, data=VocabGrowth)
idata <-data.frame(grade=ordered(8:11))
heplot(Vocab.mod, type="III", idata=idata, idesign=~grade, iterm="grade",
main="HE plot for Grade effect")
mark.H0()
# }