Some people say magic incantations are bad.
But then, you find a code snippet — sorry, incantation — on Hadley Wickham’s web site, and find out how to plot that interaction effect graph you need.
Isn’t it pretty? The bare bones:
effectdf <- function(...) {
suppressWarnings(as.data.frame(effect(...)))
}
my.xlevels=list(x=seq(0,1,0.05), rol=c(TRUE,FALSE)
both2 <- effectdf("x*z", lm.mod,xlevels=my.xlevels)
fplot <- ggplot(mapping = aes(y = fit, ymin = lower, ymax = upper)
fplot %+% both2 + aes(x=x,group=z,color=z,fill=z) + geom_smooth(stat="identity")
If you want substance, the paper in which the graph features will be uploaded in a week's time, ready for the UK PSA in Edinburgh.