R in Action, Third Edition

6 Basic graphs

This chapter covers

• Plotting data with bar, box, and dot plots
• Creating pie charts and tree maps
• Using histograms and kernel density plots

Whenever we analyze data, the first thing we should do is look at it. For each variable, what are the most common values? How much variability is present? Are there any unusual observations? R provides a wealth of functions for visualizing data. In this chapter, we’ll look at graphs that help you understand a single categorical or continuous variable. This topic includes

• Visualizing the distribution of a variable

• Comparing the distribution of a variable across two or more groups

In both cases, the variable can be continuous (for example, car mileage as miles per gallon) or categorical ...