ABSTRACT
Graphs must be displayed in two dimensions, either on paper or on a computer screen. It is therefore straightforward to show one variable plotted on a vertical axis against a second variable plotted on a horizontal axis. For example, Figure 3.1 shows the alar extent plotted against the total length for the 49 female sparrows measured by Hermon Bumpus in his study of natural selection, which has been described in Example 1.1. Such plots allow one or more other characteristics of the objects being studied to be shown as well, and in the case of Bumpus’ sparrows, survival and nonsurvival are indicated. These plots are simple and can be produced in Excel or another spreadsheet program, as well as in all standard statistical packages. The plots can also be produced using R code, provided in the Appendix to this chapter, for both this type of plot and the more complicated plots that are described below.
