Important R-functions used in the 1st lab

Packages:
-	nlme for longitudinal data
-	lattice for visualization

Useful functions in nlme:
-	reshape()
-	groupedData()
-	gls()
-	plot() for groupedData objects

General:
-	rowSums()
-	xtabs()
-	with()
-	order()
-	seq_along()
-	rbind()

lattice-functions:
-	xyplot()
-	loess()
-	panel.superpose()
-	panel.xyplot()
-	panel.loess()
-	panel.lines()
-	panel.points()