#### Overview of this book

gnuplot is the world's finest technical plotting software, used by scientists, engineers, and others for many years. It is in constant development and runs on practically every operating system, and can produce output in almost any format. The quality of its 3d plots is unmatched and its ability to be incorporated into computer programs and document preparation systems is excellent. gnuplot Cookbook ñ it will help you master gnuplot. Start using gnuplot immediately to solve your problems in data analysis and presentation. Quickly find a visual example of the graph you want to make and see a complete, working script for producing it. Learn how to use the new features in gnuplot 4.4. Find clearly explained, working examples of using gnuplot with LaTeX and with your own computer programming language. You will master all the ins and outs of gnuplot through gnuplot Cookbook. You will learn to plot basic 2d to complex 3d plots, annotate from simple labels to equations, integrate from simple scripts to full documents and computer progams. You will be taught to annotate graphs with equations and symbols that match the style of the rest of your text, thus creating a seamless, professional document. You will be guided to create a web page with an interactive graph, and add graphical output to your simulation or numerical analysis program. Start using all of gnuplot's simple to complex features to suit your needs, without studying its 200 page manual through this Cookbook.
gnuplot Cookbook
Credits
www.PacktPub.com
Preface
Free Chapter
Plotting Curves, Boxes, Points, and more
Annotating with Labels and Legends
Applying Colors and Styles
Combining Multiple Plots
Programming gnuplot and Dealing with Data
The Third Dimension
Using and Making Graphical User Interfaces
Surveying Special Topics
Finding Help and Information
Index

## Combining surfaces with images

It is possible to plot a surface and its projection as a color image on the x-y plane on the same graph. The two simultaneous views of the same data or function can be useful to bring out the topography of a complex surface.

The previous figure shows a simple trigonometric function of two variables displayed as a surface with its values simultaneously encoded into colors (or gray values) at the base of the plot.

### How to do it…

The following script produces the previous figure as its output:

set iso 40
set samp 40
unset key
set xrange [-pi:pi]
set yrange [-pi:pi]
f(x,y) = sin(x)*cos(y)
set hidden front
set xyplane at -1
splot f(x,y) with pm3d at b, f(x,y) with lines

### How it works…

The new features we are combining to produce this graph are in the highlighted lines in the code sample. Let's look at the last command first. The first part of the splot command plots the function f(), which is defined three lines above, as a colored surface at the base of the plot; this...