Chapter 8. All about axes
This chapter covers
- Using multiple axes
- Selecting plot ranges
- Customizing tic marks and tic labels
- Plotting time series with gnuplot
In this chapter, we finally come to coordinate axes and their labeling. Treating them last, after discussing plot styles and decorations, may seem surprising, given how critical well-labeled coordinate axes are to achieving an informative graph. On the other hand, gnuplot’s default behavior for axes-related options is adequate in almost all situations, so explicit customization is rarely required.
One topic deserves special consideration: the use of multiple axes on the same plot. We’ll discuss this first. Then we’ll move on and describe all the ways axes and their labels can be customized. Finally, we’ll treat the special case when one axis (usually the x axis) represents time: in other words, when the plot shows a time series. Time-series plots pose special challenges, because the labels aren’t numeric. Instead, you need to worry about things such as the names of months and weekdays—potentially in different languages! This has long been a problem to gnuplot users, so I’ll devote significant space to this application. But first, let’s talk about multiple axes on the same plot.