Appendix E. Special plots
In this appendix, we’ll discuss several “special” plotting options. All of them produce graphs that are visually and semantically more complicated than the line-and-point plots we’ve been dealing with so far.
First, you’ll learn about gnuplot’s multiplot feature. This is a way to combine different plots into a single graph. The individual components may either be arranged on a regular array (that’s the more common case) or be placed arbitrarily (for example, to create insets within a larger graph).
In the remainder of the appendix, we’ll introduce three types of plots that summarize entire data sets in some way. First, we’ll discuss box-and-whisker plots: a popular method to visualize the distribution of points in a simple and robust fashion. Then we’ll turn to parallel coordinates. This is a relatively new type of plot that’s intended to reveal structure in multidimensional data sets, but gnuplot makes them easy to create. The final section deals with gnuplot’s support for drawing histograms: pretty and popular, they’re most suitable for presentations and information graphics.
Except for the first topic (multiplot), the material in this appendix is rather specialized, and not everyone may have a need for it. Make sure you catch the multiplot features, but feel free to skip the rest if it’s not relevant to you right now.