lattice legends with groups

legends.R

# Legends and Groups in Lattice
# Bryan Urban
# 2015-06-01

library(lattice)
head(mtcars)

my.col <- c("black", "blue", "red")
my.settings <- 
  list(superpose.line    = list(col=my.col),
       superpose.polygon = list(col=my.col),
       superpose.symbol  = list(col=my.col))

g.lab <- as.character(unique(mtcars$cyl))
g.lab <- paste(g.lab, "cyl")

xyplot(mpg~hp, groups=cyl, mtcars, type='p',
       ylab = "mpg",
       xlab = "hp",
       key=list(text=list(g.lab, cex=4),# font="Helvetica"), 
                lines=list(col=my.col, width=4),
                points=list(pch=4, col=my.col),
                rect=list(col=my.col, border=F, height=0.5, size=8),
                corner=c(.9, .9), 
                # space="top",
                # space="right", 
                padding=3,
                columns=2,
                border="black",
                background="white"),       
       par.settings = my.settings
       )