This is a list of frequently asked questions (FAQ) for GNU Octave users.

We are always looking for new questions (with answers), better answers, or both. Feel free to edit this page with your changes. If you have general questions about GNU Octave, or need help for something that is not covered by the Octave manual or the FAQ, please use the help@octave.org mailing list.

This FAQ is intended to supplement, not replace, the GNU Octave manual. Before posting a question to the help@octave.org mailing list, you should first check to see if the topic is covered in the manual.

General

What is Octave?

GNU Octave is a high-level interactive language, primarily intended for numerical computations, that is mostly compatible with Matlab.

GNU Octave can do arithmetic for real, complex or integer-valued scalars and matrices, solve sets of nonlinear algebraic equations, integrate functions over finite and infinite intervals, and integrate systems of ordinary differential and differential-algebraic equations.

GNU Octave uses the GNU readline library to handle reading and editing input. By default, the line editing commands are similar to the cursor movement commands used by GNU Emacs, and a vi-style line editing interface is also available. At the end of each session, the command history is saved, so that commands entered during previous sessions are not lost.

The GNU Octave distribution includes a 650+ page Texinfo manual. Access to the complete text of the manual is available via the doc command at the GNU Octave prompt.

What is Octave-Forge?

Octave-Forge is a collection of packages for GNU Octave, something similar to the Matlab toolboxes. When talking about the two projects at the same time, GNU Octave is usually referred to as Octave core (or just core). Octave-Forge also serves as a test bed for code that may eventually end up in the core, and distributes binaries for systems with a lack of developers tools (mainly Windows).

Who uses Octave?

Lots of people. It seems that universities use it for research and teaching, companies of all sizes, for development, individuals. This question comes often on Octave mailing lists, see Who Uses Octave? for a few answers

Who develops Octave?

Discussions about writing the software that would eventually become Octave started in about 1988 with James B. Rawlings and John W. Eaton at the University of Texas. John W. Eaton was the original author of Octave, starting full-time development in February 1992. He is still the primary maintainer. The community of users/developers has in addition contributed some code and fuels the discussion on the mailing lists help@octave.org (user forum), maintainers@octave.org (development issues).

Why "Octave"?

Octave's name has nothing to do with music. It's named after Octave Levenspiel, a former professor of John who was famous for his ability to do quick back-of-the-envelope calculations. You can hear John pronounce the name "Octave" a few times in this video. We hope that GNU Octave will help perform computations with the same ease as Dr. Levenspiel.

Why GNU Octave?

The GNU Project was launched in 1984 to develop a complete Unix-like operating system which is free software: the GNU system.

GNU is a recursive acronym for “GNU's Not Unix”; it is pronounced guh-noo, approximately like canoe.

The Free Software Foundation (FSF) is the principal organizational sponsor of the GNU Project.

Octave became GNU Octave in 1997 (beginning with version 2.0.6). This meant agreeing to consider Octave a part of the GNU Project and support the efforts of the FSF. A big part of this effort is to adhere to the GNU coding standards and to benefit from GNU's infrastructure (e.g. code hosting and bug tracking). Additionally, Octave receives sponsorship from the FSF's Working Together fund. However, Octave is not and has never been developed by the FSF.

For more information about the GNU project, see http://www.gnu.org.

What version should I use?

In general, you will find the latest version on http://www.octave.org/download.html. It is recommended to use the stable version of octave for general use, and the development version if you want the latest features and are willing to tolerate instability.

A list of user-visible changes since the last release is available in the file NEWS. The file ChangeLog in the source distribution contains a more detailed record of changes made since the last release.

On what platforms does Octave run?

Octave runs on various Unices—at least Linux and Solaris, Mac OS X, Windows and anything you can compile it on. Binary distributions exist at least for Debian, SUSE, Fedora and RedHat Linuxes (Intel and AMD CPUs, at least), for Mac OS X and Windows' 98, 2000, XP, Vista, and 7.

Two and three dimensional plotting is fully supported using gnuplot and an experimental OpenGL backend.

The underlying numerical solvers are currently standard Fortran ones like LAPACK, LINPACK, ODEPACK, the BLAS, etc., packaged in a library of C++ classes. If possible, the Fortran subroutines are compiled with the system's Fortran compiler, and called directly from the C++ functions. If that's not possible, you can still compile Octave if you have the free Fortran to C translator f2c.

Octave is also free software; you can redistribute it and/or modify it under the terms of the GNU General Public License, version 3, as published by the Free Software Foundation, or at your option any later version.

Why are the developers planning to replace Gnuplot with an OpenGL backend?

The development of Octave is committed to being both compatible with Matlab and adding additional features. Toward those ends, the development community has chosen to introduce a native OpenGL backend that supports Matlab handle graphics and its uicontrols. Starting with the 3.8 release, Octave now uses OpenGL graphics by default with FLTK widgets. A Qt OpenGL toolkit is also under development.

There are no plans to remove the gnuplot backend. While a better backend may some day become the new default plotter, the gnuplot backend will still be available as long as our users find it useful.

How can I cite Octave?

Octave is free software and does not legally bind you to cite it. However, we have invested a lot of time and effort in creating GNU Octave, and we would appreciate if you would cite if you used.

Run citation at the Octave prompt for details on how to best cite the Octave version you are running. Certain Octave packages also have recommended citations in which case use citation package_name.

Ideally, you should cite the software itself, not a book or manual, like so:

 @software{octave,
   author = {John W. Eaton and others},
   title = {GNU Octave},
   url = {http://www.octave.org},
   version = {4.0.0},
   date = {2015-05-27},
 }

It is recommended to do so on a first draft submitted. However, some editors may disallow this, in which case you can still make a general reference to Octave in the text, such as:

This work made use of the free software package GNU Octave, and the authors are grateful for the support of the Octave development community.

If a more traditional reference is required, there is also a manual for each Octave release that can be cited:

 @book{,
   author    = {John W. Eaton, David Bateman, S\oren Hauberg, and Rik Wehbring},
   title     = {{GNU Octave} version 4.0.0 manual: a high-level interactive language for numerical computations},
   year      = {2015},
   url       = {http://www.gnu.org/software/octave/doc/interpreter},
 }

Note that there are two reasons for citing the software used. One is giving recognition to the work done by others which we already addressed. The other is giving details on the system used so that experiments can be replicated. This is just as important, if not more.

For this, you should cite the version of Octave and all packages used, as well as any details of your setup as part of your Methods. In addition, you should make your source available. See How to cite and describe software for more details and an in depth discussion.

When will feature X be released or implemented?

When it's ready, sooner if you help. Send us patches if you can. We like patches. If you can't, some developers may be convinced to work on your specific problem for some money.

How can I get involved in Octave development?

Be around. Be social. Participate in the help and maintainers mailing lists. Find things about Octave you don't like, and start thinking about how to fix them. Many people who now contribute to Octave first spent several years helping in the mailing list before they started to delve into the code. A good way to learn Octave is to understand the problems other people are having with it, so being helpful in the mailing lists not only helps Octave as a whole, but it also prepares you to be a better Octave contributor.

If you feel ready to dive right into the code, read here and here for guidance. But do not send an email to the mailing lists listing your skills and offering to help. We won't just suggest things for you to do. We lack volunteers and we do need your help, but because of that, we also lack the time to provide good guidance and mentoring. If there is a specific short-term project you would like to work on, say so, and just do it. Then ask for help or advice when you're doing it. It is a lot more important that you do something that you're actually interested on than something we suggested because it only matches your skills.

We also need help with this wiki and the manual. These are also important tasks. The documentation is easy to patch, and the help text for individual functions even more so. Editing this wiki is even easier.

Accurate bug reporting is also very useful. Find and report bugs, making an attempt to diagnose them. Eventually, you will also know how to fix them. If you want to help with bug reports or patches, subscribe to the bug tracker mailing list. You'll get updates on all bug activity, and you can jump in when you see something you can help with.

Look at our Projects and Summer of Code Project Ideas if you need specific inspiration for coding tasks that we would like to get done. See also the list of short projects.

Licensing issues

If I write code using Octave do I have to release it under the GPL?

The answer depends on precisely how the code is written and how it works.

Code written entirely in the scripting language of Octave (interpreted code in .m files) may be released under the terms of whatever license you choose.

Code written using Octave's native plug-in interface (also known as a .oct file) necessarily links with Octave internals and is considered a derivative work of Octave and therefore must be released under terms that are compatible with the GPL.

Code written using Octave's implementation of the Matlab MEX interface may be released under the terms of whatever license you choose, provided that the following conditions are met:

The plugin should not use any bindings that are specific to Octave. In other words, the MEX file must use the MEX interface only, and not also call on other Octave internals. It should be possible in principle to use the MEX file with other programs that implement the MEX interface (e.g., Matlab).
The MEX file should not be distributed together with Octave in such a way that they effectively create a single work. For example, you should not distribute the MEX file and Octave together in a single package such that Octave automatically loads and runs the MEX file when it starts up. There are other possible ways that you might effectively create a single work; this is just one example.

A program that embeds the Octave interpreter (e.g., by calling the "octave_main" function), or that calls functions from Octave's libraries (e.g., liboctinterp, liboctave, or libcruft) is considered a derivative work of Octave and therefore must be released under terms that are compatible with the GPL.

Since the MEX interface allows plugins to be distributed under terms that are incompatible with the GPL, does this mean that you are encouraging people to write non-free software for Octave?

No. The original reason for implementing the MEX interface for Octave was to allow Octave to run free software that uses MEX files (the particular goal was to run SundialsTB in Octave). The intent was to liberate that software from Matlab and increase the amount of free software available to Octave users, not to enable people to write proprietary code for Octave. For the good of the community, we strongly encourage users of Octave to release the code they write for Octave under terms that are compatible with the GPL.

I wrote a program that links with Octave libraries and I don't want to release it under the terms of the GPL. Will you change the license of the Octave libraries for me?

No. Instead of asking us to change the licensing terms for Octave, we recommend that you release your program under terms that are compatible with the GPL so that the free software community can benefit from your work the same as you have benefited from the work of all the people who have contributed to Octave.

Why can't I use code from File Exchange in Octave? It's released under a BSD license!

When one downloads code from File Exchange and use it on non Mathworks software (such as Octave), they are violating the Matlab central Terms of Use. While the BSD licenses does allow one to use such code in Octave, it also allows others to further impose restrictions which Mathworks does through the MATLAB Central Terms of Use of their site:

Content submitted to File Exchange may only be used with MathWorks products.
—Matlab central, Terms of Use 2iii

It should suffice -- although interpretations of this vary -- to contact the author directly and have them send you the code personally, or download the code from the author's own website, if available.

If you need that code or think that the code is useful, please write the authors asking them to release under a free license. Some examples of letters/email sent to authors can be found in the page Asking for package to be released under GPL: examples.

Feel free to remix and reuse, just make sure you use your name!

What's new in Octave

Each new Octave release introduces many new features. The following are a distilled list of the major changes. A complete list of user visible changes can be seen by running news at the Octave prompt, and a full list of changes is on the Template:Filepath distributed with the Octave sources.