The Personal Web Pages of Chris X. Edwards

gradu - Graphics Dump

Some example output:

CONCEPT

The idea for gradu came from the frustration of not being able to plot simple datasets of 2d vectors. I was doing some experiments with vector geometry which produced quite a lot of data and I couldn't find a simple way to have a look at it graphically. I found the GNU plotutils package which seemed very promising, but its included program, graph, was rather heavily oriented to X vs. Y style "graphs". My requirements were much less structured and certainly not oriented towards traditional mathbook graphs.

The libplot library contained exactly the functionality I was looking for, but I couldn't find a program that put it to use in a general way. I'm sure opinions vary, but I believe that a program like "graph" should be two parts. One part to calculate where all the lines of a particular graph are and another part to actually plot it. gradu is an attempt to be this second stage.

With gradu, a user has most of the functionality of the libplot library without either having to write their own C program, or circumventing the intent of a program like "graph" to get unorthodox results.

A program could be written that generated graphs and then fed the geometry data to gradu. I'll leave that for someone else. Another example is the follow up program I wrote, vmaster, which takes 3d data sets and evaluates them to 2d data sets. By piping vmaster's output to gradu, one can input a stream of 3d vector geometry and see an image as a result. All of this is inspired by the very modular Unix way of doing business.

STRATEGY

The idea for functionality was to have a system that was as flexible as possible for a wide variety of sensible input styles. I was particularly attentive to the case where a list of coordinates streams is unattended by anything else. This creates the functionality of a dot-to-dot experience. From this simplist case, the input stream can optionally be embellished to provide things like relocating the pen, relative coordinates, true arcs, properties, text, and more.

One of the keys to the flexibility is the parsing routine. The general strategy is that characters that aren't relevant get replaced with spaces and spaces are the delimiters. This means that whatever crazy syntax your input may have, there probably isn't a lot that needs to be done with it to make it work out. Certainly a quick visit to the sed command should be able to cure any problems.

The libplot library is pretty elaborate. There are a lot of fancy features. This required that the data be able to specify commands for various fancy operations. These single letter commands can be placed anywhere in the input line. The numeric values supplied, if any, will of course need to be in the correct order, but this really provides a huge degree of flexibility.

Data can be specified as files on the command line or piped in using the finest Unix traditions. Default output produces an X window with the data plotted. When making output files such as postscript or gifs, simply redirect output to the desired file name using the Unix ">".

CAVEATS

I wrote this program with a fairly simple problem at hand. I did try to do it right and lay the foundation for a very good system. The fact remains that once I got it doing what I needed it to do, I didn't get too crazy about testing all the other functionality. This includes things like text handling, widths, and styles. I also have noticed a problem when animating in X. It can cause some kind of infinite loop. I was content with gif animations and they work fine, so no serious debugging was done with the X ones. Sorry kids.

UPDATES

2003.02.07: When I first wrote this, I didn't bother with libplot's ability to use rotated text. I figured, who would need that? Well, sure enough, I needed it. So I added it. I also fixed an ugly little thing that caused a warning when using text.

DOWNLOAD

The program is available here: gradu-1.19.tgz

It is only 18kB and includes some simple example data.

Also, you can check out the capabilities of gradu by looking at the html man page for gradu.

This program is really a way to show off the abilities of the GNU Plot Utilities. This means that you need to have libplot installed and ready to link to. To get this library, have a look here: http://www.gnu.org/software/plotutils/plotutils.html

LEGAL NONSENSE

This program is released under the GNU General Public License (GPL). It is so flawed that it should be considered dangerous to whatever you're doing, your data, your physical computer, your health, and sanity. Do not use it under any circumstances. I am not responsible for any silly thing either you or I do with regard to this program.

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Chris X. Edwards ~ May 2002