Chapter 2. Packages and Help Pages

You now have a function that simulates rolling a pair of dice. Let’s make things a little more interesting by weighting the dice in your favor. The house always wins, right? Let’s make the dice roll high numbers slightly more often than it rolls low numbers.

Before we weight the dice, we should make sure that they are fair to begin with. Two tools will help you do this: repetition and visualization. By coincidence, these tools are also two of the most useful superpowers in the world of data science.

We will repeat our dice rolls with a function called replicate, and we will visualize our rolls with a function called qplot. qplot does not come with R when you download it; qplot comes in a standalone R package. Many of the most useful R tools come in R packages, so let’s take a moment to look at what R packages are and how you can use them.


You’re not the only person writing your own functions with R. Many professors, programmers, and statisticians use R to design tools that can help people analyze data. They then make these tools free for anyone to use. To use these tools, you just have to download them. They come as preassembled collections of functions and objects called packages. Appendix B contains detailed instructions for downloading and updating R packages, but we’ll look at the basics here.

We’re going to use the qplot function to make some quick plots. qplot comes in the ggplot2 package, a popular package for making graphs. Before you ...

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