Add dataset potatoyield (Pimentel, page 76).

data-raw/potatoyield.R

+##----------------------------------------------------------------------
+## Data generation.
+
+potatoyield <- read.table("http://www.leg.ufpr.br/~walmes/data/pimentel_batatinha.txt",
+                          header=TRUE, sep="\t")
+names(potatoyield) <- c("block", "variety", "yield")
+str(potatoyield)
+
+potatoyield <- potatoyield[with(potatoyield, order(block, variety)),]
+
+save(potatoyield, file="../data/potatoyield.RData")
+
+##----------------------------------------------------------------------
+## Examples.
+
+require(lattice)
+
+xyplot(yield~variety, data=potatoyield,
+       groups=block, type="o",
+       ylab=expression(Yield~(t~ha^{-1})),
+       xlab="Variety")
+
+rm(list=ls())
+load("../data/potatoyield.RData")
+ls()
+str(potatoyield)