diff --git a/data-raw/plowing.R b/data-raw/plowing.R
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+##----------------------------------------------------------------------
+## Data generation.
+
+plowing <- read.table("http://www.leg.ufpr.br/~walmes/data/pimentel_aradura.txt",
+                      header=TRUE, sep="\t")
+names(plowing) <- c("plow", "block", "yield")
+levels(plowing$plow) <- c("normal", "deep")
+str(plowing)
+
+plowing <- plowing[with(plowing, order(block, plow)),]
+
+save(plowing, file="../data/plowing.RData")
+
+##----------------------------------------------------------------------
+## Examples.
+
+require(lattice)
+
+xyplot(yield~plow|block, data=plowing, type=c("p", "a"),
+       ylab=expression(Yield~(t~ha^{-1})),
+       xlab="Plowing level")
+
+rm(list=ls())
+load("../data/plowing.RData")
+ls()
+str(plowing)
diff --git a/data/plowing.RData b/data/plowing.RData
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