# ANALYTICPIC

ANALYTICPIC is a program, written in MATLAB, which creates pictures of complex-valued functions of a complex variable. MATLAB can create good three-dimensional pictures, but four degrees of freedom are needed to make the kind of images in question. Colour is used as the fourth degree of freedom: A graph drawn by ANALYTICPIC is a coloured surface. The modulus of a function is given by the height of the graph, and the argument is given by the colour of the appropriate point on the graph. (Roughly speaking, light blue corresponds to positive real values, red to negative real values, purply-blue to positive purely imaginary values, and greeny-yellow to negative purely imaginary values.)

Here are some examples of graphs drawn by ANALYTICPIC:

### How to get a copy of ANALYTICPIC

If you have MATLAB, you should be able to use ANALYTICPIC. Here's how to get a copy:

• If you are in the Math Department at the University of Washington, contact Don Marshall (`marshall@math`), who can give you a copy.
• If you aren't in the Math Department at UW, there's a bit of a hitch: ANALYTICPIC makes use of a program called `pderot3d`, which is part of MATLAB's PDE toolbox.

If you have the PDE toolbox, this is pretty easy to work around: get a tarred version of ANALYTICPIC (by clicking on the link below). When you untar the file, you will find a text file called `pdechanges.txt`, which details some changes to make to `pderot3d`. These changes make `pderot3d` work a little better for ANALYTICPIC.

If you don't have the PDE toolbox, you'll still be able to use ANALYTICPIC, but without one of its more useful features: the ability to rotate the graph using the mouse. If you want to do this, first get a tarred version of ANALYTICPIC (by clicking on the link below). Then, in the file `drawgraph.m`, either remove or comment out the following line:

`if dp==0 pderot3d on; end`

ANALYTICPIC should now work for you. You should even be able to change the viewpoint of the graphs you get, albeit in a clumsy manner, by using MATLAB's `view` command.

Tarred version of ANALYTICPIC

Currently, ANALYTICPIC has only been tested on Unix. It would be nice to know if it works on other platforms.

If you have any comments, suggestions, bug reports, or good examples, please send them to Paul Moorehead