In this chapter, you learned a variety of useful techniques to produce high-quality graphs using qplot. You also learned how to create scatterplots, line graphs, and many other types of graph. You also saw how useful qplot can be when you want to map symbol size, shape, and color (or linetype) to levels of a categorical variable. In a book of this scope, it is impossible to cover all of the possibilities available through qplot, but I hope you found that this chapter provided helpful approaches that you can use to create your own graphs. Many books and online sources on qplot are available for you to develop your qplot skills even further.

In the next chapter, you will learn how to create graphs using the ggplot function, an even more powerful graphics command.