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FAQ

• About traj
• What is traj?
• What documentation is available?
• Who did this?
• Why "traj?"
• How is traj licensed?
• What can traj do?
• What kind of equations can you plot?
• What can be plotted?
• How come traj cannot do *?
• Obtaining and Installing traj.
• Where can I get traj?
• Using traj.
• Has this been used in a classroom?
• How is traj licensed?
• Can I use this in my class?
• Can I use this at work?
• Misc.
• How is this possible?
• What's wrong with you?

About traj

• What is traj?
  

  traj is a program designed to plot the solutions of systems of ordinary differential equations in phase space. The solutions are found either through numerical approximations or by reading data files (text format). Different numerical approximations are available including Runge-Kutta, Euler, and others.

• What documentation is available?
  

  The documentation is written in LaTeX. The documentation is available under the GNU public documentaion license, and the source files come with the standard distribution. A copy of the documentation is available in pdf format as well. The specifics can found on the documentation page.

• Who did this?
  

  I did. My name is Kelly Black, and I am a professor of mathematics at Union College.

• Why "traj?"
  

  Because it is a nice little program that allows you to visualize the solutions of ordinary differential equations (ODEs). Not only that it is free and easy to use

  Or did you mean why the name? The program plots the trajectories of the solutions to ODEs. The word traj is easier to type than trajectory.

• How is traj licensed?
  

  The program is licensed under the GNU public license. You are free to copy this program and make whatever changes you like. The only stipulation is that you have to make your work available and give me some credit. Also, the documentation is made available via the GNU public document license which means that you can make any additions or changes that is appropriate for your site.

What can traj do?

• What kind of equations can you plot?
  

  The program is designed to plot the trajectories of the solutions of ordinary differential equations (ODEs). You can type in the differential equations, and the program will generate an approximation. The program can also read data files (text format). The program is simple but is also quite flexible.

• What can be plotted?
  

  The program plots trajectories. See above for how to generate the trajectories.

• How come traj cannot do *?
  

  Because I am too lazy. There are a lot of features that I would like to add. Unfortunately, there is also a long list of other things I need to do as well. Perhaps I spend too much time with my daughter, but I will get around to other features eventually.

Obtaining and Installing traj.

• Where can I get traj?
  

  The files associated with this software can be found at the sourceforge project page. The folks at sourceforge have made the process of developing and distributing this software much easier, and they deserve a big thank you!

Using traj.

• Has this been used in a classroom?
  

  Yes. It has been used in a second year differential equations class. It is used to demonstrate the ideas of stabilty and fixed points. The ability to see the solution in 3D phase space is a big help in helping the students see what the issues are.

• How is traj licensed?
  

  Please see the license section.

• Can I use this in my class?
  

  Yes! Please! If you think that this might be useful we fully encourage you to give it a try.

• Can I use this at work?
  

  Yes. It is a free license!

Misc.

• How is this possible?
  

  I put a lot of work into it! There is also a big community that makes it possible for me to concentrate on the program itself. For example, the tools available at sourceforge make it possible to do the development. Also, the gui is possible because of the work of the folks who developed gtk+. The 3D graphics are made possible through the availability of opengl. On our systems this done through the use of mesa.

  Finally, the availabity of gtkglarea by * has been a huge help. It allowed me to focus on the program and not play around with widgets. It is unfortunate that gtkglarea is no longer maintained. It is a robust and easy tool that saved a lot of heartache.

  Without the help of this surprisingly large and complex community small projects like this would not be possible.

• What's wrong with you?
  

  I dunno.