: 
if (require(ggplot2)){
  qplot(Time, Weight, data=dietox, col=Pig) + geom_line() +
        theme(legend.position = "none") + facet_grid(Evit~Cu)
} else {
  coplot(Weight ~ Time | Evit * Cu, data=dietox)
}

## End(Not run)
</code></pre>

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