Gnuplot in Action, Second Edition

Appendix C. Surface and contour plots

The plot command discussed in this book creates graphs that show how one variable (y) behaves as a function of another one (x). But what if you want to show how some quantity depends on two independent variables? In other words, how can you best visualize a single “output” variable as a function of two “input” variables? That’s basically the problem cartographers have: show a quantity (the elevation above sea level or the type of ground cover) as a function of two coordinates (the position on the surface). In gnuplot, you have essentially the same options cartographers have:

• Create a rendering of a raised surface. Cartographers call this a relief map; I’ll refer to it as a surface plot.
• Create a contour ...