R help - Mar 2016 - Trouble plotting interaction with brkdn.plot from plotrix package

Hello,

I'm exploring different ways to plot interactions for mixed-design ANOVA and
am having difficulty getting the brkdn.plot() function in the R plotrix package
to work.

The interaction.plot() is working fine, but I'd really like to be able to
customize the plot more as the brkdn.plot() function seems to be able to do.

Any help pointing out my error(s) would be much appreciated.

Pete Miksza

IU Jacobs School of Music, Bloomington, IN

Here is an example of my code:

set.seed(1976)
Y = rnorm(1600, 5, 2)
A = c(rep(1, 200), rep(2, 200), rep(1, 200), rep(2, 200), rep(1, 200), rep(2,
200), rep(1, 200), rep(2, 200))
B = c(rep(1, 400), rep(2, 400), rep(3, 400), rep(4, 400))
A = factor(A, levels = c(1, 2), labels = c("Treat",
"Control"))
B = factor(B, levels = c(1, 2, 3, 4), labels = c("One",
"Two", "Three", "Four"))
dat = data.frame(Y, A, B)
str(dat)

# I can't figure out why this doesn't work
library(plotrix)
brkdn.plot("dat$Y", "dat$B", "dat$A", data = dat)

# this works
interaction.plot(dat$B, dat$A, dat$Y, fun = mean)

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