# Changes

## FAQ

, 23:30, 22 October 2019
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 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 =Where do I get additional help?= If you can't find an answer to your question in this FAQ is intended to supplement, not replacewiki, or in the Octave [http://www.octave.org/doc/interpreter manual] ([http://www.octave.org/octave.pdf PDF]) you can: * Search for an answer in our [https://lists.gnu.org/archive/html/help-octave/ mailing list archives]* Contact our user community using our [https://lists.gnu. Before posting a question to the org/mailman/listinfo/help-octave help@octave.org mailing list, you should first check ] (feel free to subscribe to see if the topic is covered this mailing list)* Contact our user community using our [https://webchat.freenode.net/?channels=octave IRC chat room <code>#octave</code> in the manual.Freenode] <div class="tocinline">__TOC__</div>
=General=
==What is Octave?==
[https://www.gnu.org/software/octave/ GNU Octave ] is a high-level interactive interpreted language, primarily intended for numerical computations that . It provides capabilities for the numerical solution of linear and nonlinear problems, and for performing other numerical experiments. It also provides extensive graphics capabilities for data visualization and manipulation. GNU Octave is normally used through its interactive interface ([https://en.wikipedia.org/wiki/Command-line_interface CLI] and [https://en.wikipedia.org/wiki/Graphical_user_interface GUI]), but it can also be used to write non-interactive programs. The GNU Octave language is mostly compatible with quite similar to Matlabso that most programs are easily portable.1
The GNU Octave can do arithmetic for real, complex or integer-valued scalars and matrices, solve sets distribution includes a [http://www.octave.org/octave.pdf 1000+ page Texinfo manual]. Access to the complete text of nonlinear algebraic equations, integrate functions over finite and infinite intervals, and integrate systems of ordinary differential and differential-algebraic equationsthe manual is available via the <code>doc</code> command at the GNU Octave prompt.
==What is 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.Forge?==
The [https://octave.sourceforge.io/ Octave distribution includes Forge] is a 650+ page Texinfo manual. Access collection of [[packages]] for GNU Octave, something similar to the complete text of Matlab toolboxes. When talking about the manual is available via the doc command two projects at the same time, GNU Octave promptis 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 Universities use it for research and teaching, companies of all sizes, for development, and individualsfor whatever private purpose. This question comes often on Octave mailing lists, see 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 [http://jweaton.org/ John W. Eaton ] at the University of Texas. John W. Eaton was is the original author of Octave, starting full-time development in February 1992. He is still the primary maintainer. The community of users/and developers has in addition contributed some code and fuels the discussion on the mailing lists [https://lists.gnu.org/mailman/listinfo/help-octave help@octave.org ] (user forum), [https://lists.gnu.org/mailman/listinfo/octave-maintainers maintainers@octave.org ] (development issues), and octave-dev@lists.sourceforge.net (all things related to the Octave Forge repository of user-contributed functions).
==Why '''GNU''' "Octave"?==
The GNU Project Octave's name has nothing to do with music. It is named after [http://en.wikipedia.org/wiki/Octave_Levenspiel Octave Levenspiel], a former professor of John who was launched in 1984 famous for his ability to develop do quick back-of-the-envelope calculations. You can hear John pronounce the name "Octave" a complete Unix-like operating system which is free softwarefew times [http: //videolectures.net/mloss08_eaton_oct/ in this video]. We hope that GNU Octave will help perform computations with the GNU systemsame ease as Dr. Levenspiel.
==Why "GNU is a recursive acronym for “GNU's Not Unix”; it is pronounced guh-noo, approximately like canoe." Octave?==
The Free Software Foundation (FSF) [https://www.gnu.org/ GNU Project] was launched in 1984 to develop a complete Unix-like operating system which is free software: the principal organizational sponsor of the GNU Projectsystem. GNU is a recursive acronym for "GNU's Not Unix"; it is pronounced [https://www.gnu.org/gnu/pronunciation.en.html g'noo].
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 The [httphttps://www.gnufsf.org/prep/standards/standards.html GNU coding standards] and to benefit from GNU's infrastructure Free Software Foundation (e.g. [http://hg.savannah.gnu.org/hgweb/octave/ code hosting] and [http://bugs.octave.org bug tracking]FSF). Additionally, Octave receives [https://my.fsf.org/donate/working-together/octave sponsorship] from is the FSF's Working Together fund. However, Octave is not and has never been developed by principal organizational sponsor of the FSFGNU Project.
For more information about Octave became GNU Octave in 1997 (beginning with [[Release History|version 2.0.6]]). This meant agreeing to consider Octave a part of the GNU project, see httpProject and support the efforts of the FSF. A big part of this effort is to adhere to the [https://www.gnu.org/prep/standards/standards.html GNU coding standards] and to benefit from GNU's infrastructure (e.g. [https://hg.savannah.gnu.org/hgweb/octave/ code hosting] and [http://bugs.octave.org bug tracking]). Additionally, Octave receives [https://my.fsf.org/donate/working-together/octave sponsorship] from the FSF's Working Together fund. However, Octave is not and has never been developed by the FSF.
==What version should How can I usecite Octave?==
In general, Octave is free software and does not legally bind you will find the latest version on http://wwwto cite it.octave.org/download.html. It is recommended to use the stable version However, we have invested a lot of octave for general usetime and effort in creating GNU Octave, and the development version we would appreciate if you would cite if you want the latest features and are willing to tolerate instabilityused. To cite GNU Octave in publications use:
A list of user John W. Eaton, David Bateman, Søren Hauberg, Rik Wehbring ({{Release Year}}). GNU Octave version {{Release}} manual: a high-visible changes since the last release is available in the file NEWSlevel interactive language for numerical computations. The file ChangeLog in the source distribution contains a more detailed record of changes made since the last release URL https://www.gnu.org/software/octave/doc/v{{Release}}/
==On what platforms does Octave run?==A [https://en.wikipedia.org/wiki/BibTeX BibTeX] entry for [https://en.wikipedia.org/wiki/LaTeX LaTeX] users is:
@manual{, title = {{GNU Octave runs on various Unices—at least Linux and Solaris, Mac OS X} version {{Release}} manual: a high-level interactive language for numerical computations}, Windows and anything you can compile it on author = {John W. Binary distributions exist at least for Debian, SUSE, Fedora Eaton and RedHat Linuxes (Intel David Bateman and AMD CPUs, at least), for Mac OS X S{\o}ren Hauberg and Windows' 98Rik Wehbring}, 2000 year = <span>{</span>{{Release Year}}}, XP, Vista url = {https://www.gnu.org/software/octave/doc/v{{Release}}/}, and 7. }
Two and three dimensional plotting is fully supported using gnuplot and an experimental OpenGL backendRun {{manual|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 <code>citation package_name</code>.
The underlying numerical solvers Note that there are currently standard Fortran ones like LAPACK, LINPACK, ODEPACK, two reasons for citing the BLAS, etcsoftware used., packaged in a library of C++ classes One is giving recognition to the work done by others which we already addressed. If possible, the Fortran subroutines are compiled with The other is giving details on the system's Fortran compilerused so that experiments can be replicated. For this, you should cite the version of Octave and called directly from all packages used (you can get this information using the C++ functions<code>ver</code> command), as well as any details of your setup as part of your Methods. If that's not possible In addition, you can still compile Octave if should make your source available. See [http://software.ac.uk/so-exactly-what-software-did-you have the free Fortran -use How to C translator f2ccite and describe software] for more details and an in depth discussion.
We also need help with Besides this wiki and , the GNU Octave distribution includes a [http://www.octave.org/doc/interpreter 1000+ page Texinfo manual] ([http://www.octave.org/octave. These are also important taskspdf PDF]). The documentation Access to the complete text of the manual is easier to patch, so available via the {{manual|doc}} command at the GNU Octave prompt. If you can discuss improvements to it and submit patches. Or just edit have problems using this wiki! Accurate bug reporting manual, or find that some topic is also very useful. Find and not adequately explained, indexed, or cross-referenced, please report it on http://bugs, making an attempt to diagnose them. Eventually, you will also know how to fix themoctave.org.
If you want to help with ==How can I report a bug reports or patches, subscribe to [https://savannah.gnu.org/mail/in Octave?group=octave 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.=
Also look at Please read our [[Projects]], the [[ESA Summer of Code in Space]], and [[GSoC Project Ideas|GSoC Project]] ideas if you need specific inspiration for coding tasks that we would like to get donewebsite http://www.octave.org/bugs.html.
=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 [https://www.gnu.org/software/octave/doc/interpreter/Oct_002dFiles.html Octave's native plug-in code interface ] (also known as a .oct file) necessarily links with Octave internals and is considered a derivative work of Octave and therefore . Therefore it must be released under terms that are compatible with the [https://www.gnu.org/licenses/gpl.html GPL].
* Code written using [https://www.gnu.org/software/octave/doc/interpreter/Mex_002dFiles.html 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 MEX file may not use any bindings that are specific to Octave. In other words, the MEX file must '''it has to use the MEX interface only'''. In other words, and not also call on other Octave internals. It it should be possible in principle to use the MEX file with other programs that implement the MEX interface (e.g., Matlab). For example including an Octave header file or calling an Octave function within the MEX file, that is not related with Octave's implementation of the MEX interface make the MEX file a derivative work of Octave and has therefore to be released under terms that are compatible with the [https://www.gnu.org/licenses/gpl.html GPL].:# The MEX file should may 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 to effectively create a single work; this is just one example.
A program * Code that '''embeds the Octave interpreter ''' (e.g., by calling the "<code>octave_main" </code> 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 Will you change the MEX interface allows plugins to be distributed under terms that are incompatible with license of the GPL, does this mean that you are encouraging people to to write non-free software Octave libraries for Octaveme?==
'''No. The original reason for implementing the MEX interface for Octave was to allow Octave ''' Instead of asking us to run free software that uses MEX files (change 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 licensing terms for Octave. For the good of the community, we strongly encourage users of Octave to recommend that you release the code they write for Octave your program under terms that are compatible with the GPL. This way 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.
==Should I wrote a program that links with Octave libraries and I don't want favor the MEX interface to release it under the terms of avoid the GPL. Will you change the license of the Octave libraries for me?==
'''No. Instead ''' The original reason for implementing the [https://www.gnu.org/software/octave/doc/interpreter/Mex_002dFiles.html MEX interface] for Octave was to allow Octave to run free software that uses MEX files (the particular goal was to run [https://computation.llnl.gov/projects/sundials/release-history#sundialsTB sundialsTB] in Octave). The intent was to liberate that software from Matlab and increase the amount of asking us free software available to Octave users, not to enable people to change the licensing terms write proprietary code for Octave. For the good of the community, we recommend that you strongly encourage users of Octave to release your program the code they write for Octave under terms that are compatible with the [https://www.gnu.org/licenses/gpl.html 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!==
{{quoteQuote|text=Content submitted to File Exchange may only be used with MathWorks products.|sign=Matlab central|source=§ 2(a)(iii) [httphttps://www.mathworks.co.ukcom/matlabcentral/termsofuse.html#content Terms of Use 2iii]}}
While That does not apply to GNU Octave, therefore the usage is in general prohibited. It should suffice — although interpretations of this vary, it should be safe to use the code if you contact the author directly and have him to send you the code personally(maybe released under a free license), or download the code from the author's own website, if available. [[Asking_for_package_to_be_released_under_GPL:_examples|Some examples of letters/email sent to authors for that purpose]].
=What's new in Octave===What's new in version series 3.6.N and 3.7.N of Octave=Installation=
Several new features have been added to the 3.6.N series. The full details are in the NEWS file, but in brief 3.6.N series brings:==How can I install Octave on Windows?==
* Perl compatible regular expressions* A profiler has been added.* Broadcasting enabled :''See: [[Octave for all built-in binary element-wise operators.* The statistical distribution functions have been overhauled.* The functions strread(), textscan(), and textread() have been rewritten.* Performance of all m-file string functions has been improved.* The qhull geometry functions have been revamped.* Date/time functions have been updated.* Matlab compatible preference functions have been added.* Various handle graphics functions have be introduced.* The parfor keyword is now recognized.Microsoft Windows]]''
==Features added in version series 3.4.N and 3.5.N of How can I install Octaveon macOS?==Here are some features that have been around since 3.4.N
* Many improvements to native OpenGL plotting* ARPACK now distributed with :''See: [[Octave* Indexing optimisations* FTP object using libcurl* Better consistency with ismatrix, issquare, and issymetric* Function handles aware of overloaded functions* More efficient matrix division by making a single LAPACK call* Other optimisations in matrix operations* bsxfun optimised for basic arithmetic functions* Matlab-style ignoring of output arguments using {{Codeline|~}}* Many optimisations of the accumarray function* Sparse matrix indexing has been rewritten for speed* Configuration pseudo-variables like page_screen_output accept a "local" option argument to limit their scope to function scope* The pkg command now accepts a -forge option to pull packages directly from Octave-forge* Several dlmread improvements* Octave now uses gnulib for better cross-platform compatibilitymacOS]]''
==Features added in version series 3.2.N and 3.3.N of How can I install Octaveon GNU/Linux?==Here are some features that have been around since 3.2.N
* integer types* fixed point arithmetic* sparse matrices* linear programming code based on GLPK* 64-bit compilation support* gzipped files and stream and consequently support of Matlab v7 files* better support :''See: [[Octave for both msvc and mingw* a fully compatible MEX interface* many many other minor features and compatibility changes* an experimental OpenGL graphics toolkit to replace gnuplot* object orient programming* block comments* imwrite and imread (based on the GraphicsMagick library)* Lazy transpose <brGNU/> Special treatment in the parser of things like "aLinux]]'' * b", where the transpose is never explicitly formed but a flag is rather passed to the underlying LAPACK code.* Single precision type* Improved array indexing <br/> The underlying code used for indexing of arrays has been completely rewritten and so the indexing of arrays is now significantly faster.
==Features available since 2.1.NHow can I install Octave on Android / what is this Octave app in the Google Play store?==Here are some older features that have been around since 2.1.N:
* NDArrays* cellsThere is an '''unofficial''' Octave app available for Android in the Google Play store. Please see [[Octave for Android]] for more information.
==Coming in a future releaseHow can I install Octave on platform X?==The 3.7.N series is the current development release and will become a 3.8.N release in the future. This series brings the following new features:
* JIT compiling in the interpreter (speeds up loops)* Octave currently runs on [[Octave for GNU/Linux|GNU/Linux]], [[Octave for macOS|macOS]], and [[Octave for Microsoft Windows|Windows]]. A GUI for It should be possible to make Octave (based work on Qt4)* The default graphics toolkit it planned other systems as well. If you are interested in porting Octave to be changed from Gnuplot to an OpenGL fltk toolkitother systems, please contact the maintainers development mailing list [https://lists.gnu.org/mailman/listinfo/octave-maintainers maintainers@octave.org].
==What documentation exists for Octaveversion should I use?==
Besides For general use, it is recommended to use the current wikilatest stable version of Octave (currently {{Release}}), there are other important sources of documentation available from http://www.octave.org/download.html. For development and help for Octavebleeding-edge features one can obtain the development source code from the Mercurial repository https://hg.savannah.gnu.org/hgweb/octave/graph/.
==What documentation exists for The used version of Octave?==is available via the {{manual|ver}} command and a list of user-visible changes since the last release is available via the {{manual|news}} command at the GNU Octave prompt.
The ==On what platforms does Octave distribution includes a 650+ page manual that is also distributed under the terms of the GNU GPL. It is available on the web at http://www.gnu.org/software/octave/doc/interpreter/ and you will also find there instructions on how to order a paper version.run?==
The complete text of the Octave manual is also available using the runs on any platform you can compile it on. Binary distributions exist for [[Octave for GNU Info system via the /Linux|GNU Emacs/Linux]], info[[Octave for macOS|macOS]], or xinfo programsand [[Octave for Microsoft Windows|Windows]]. To work fully functional, or by using Octave requires the {{Codeline|doc}} command used platform to start support the GNU underlying numerical libraries like [https://en.wikipedia.org/wiki/Basic_Linear_Algebra_Subprograms BLAS], [https://en.wikipedia.org/wiki/LAPACK LAPACK], [http://www.suitesparse.com SuiteSparse], etc., and for plotting [https://www.opengl.org/ OpenGL] or [http://www.gnuplot.info browser directly from the Octave prompt/ gnuplot].
If you have problems using this documentation, or find that some topic is not adequately explained, indexed, or cross-referenced, please report it on http://bugs.octave.org.==How can I obtain Octave's source code?==
If you can't find an answer to your question, the help@* https://www.octave.org mailing list is available for questions related to using, installing, and porting Octave that are not adequately answered by the Octave manual or by this document/download.html* https://ftp.gnu.org/gnu/octave/
==User community==Since Octave is distributed under the terms of the GPL, you can get Octave from a friend who has a copy.
To subscribe to ==How can I build Octave from the list, go to http://www.octave.org/archive.html and follow the link to the subscription page for the list.source code?==
Please do To use Octave it is usually not send requests required to be added or removed build it from the mailing listit's source code. Binary distributions exist for [[Octave for GNU/Linux|GNU/Linux]], or other administrative trivia to the list itself[[Octave for macOS|macOS]], and [[Octave for Microsoft Windows|Windows]].
An archive of old postings If you have reasons to build Octave from the help-octave mailing list is maintained on http://www.octave.org/archive.htmlsource code, see [[Building]] for more information.
You will also find some user advice and ==What do I need to build Octave from the source code spread over the web. Good starting points are the Octave Wiki http://wiki.octave.org and Octave-Forge http://octave.sourceforge.net?==
We also have For a list of build dependencies see [http://www.octave.org/chat.html an IRC chat room[Building]].
==Do I think I have found a bug in need GCC to build Octave.from the source code?==
“I No. The development is done primarily with [https://gcc.gnu.org/ GCC], so you may hit some incompatibilities. Octave is intended to be portable to any standard conforming compiler (for example [https://clang.llvm.org/ clang] is know to work as well). If you have difficulties that you think I have found a are bugs, please report them to the [http://bugs.octave.org bug in Octavetracker], but I'm not sureor ask for help on the [https://lists.gnu.org/mailman/listinfo/help-octave help@octave.org mailing list]. How do I know, and who should I tell?”
First, see the section [http://www.octave.org/bugs.html on bugs and bug reports =What's new in the Octave manual]. When you report a bug, make sure to describe the type of computer you are using, the version of the operating system it is running, and the version of Octave that you are using. Also provide enough code and configuration details of your operating system so that the Octave maintainers can duplicate your bug.?=
=How Each new Octave release introduces many new features. A complete list of user visible changes can I obtain be seen by running <code>news</code> at the Octave?=prompt. The following changes are a distilled list of the major changes:
==Source codeWhat's new in the next version of Octave?==
Source code is available See the [http://hg.savannah.gnu.org/hgweb/octave/file/tip/NEWS NEWS file] on the Octave development site, where you are sure to get the latest versionbranch.
Since Octave is distributed under See the terms of complete user-visible changes on the GPL, you can get Octave from a friend who has a copy, or from the Octave website[https://www.gnu.org/software/octave/NEWS-4.0.html NEWS file].
==Pre-compiled binary packages==* First official release of the GUI.* Release of official windows binaries.* Experimental support for [[classdef]].* OpenGL graphics with Qt widgets.* Several functions for reading, writing, and recording of audio.
The Octave project does not distribute binary packages, but other projects do==What's new in version series 3.8. For an up-to-date listing X of packagers, see:Octave==
* httpSee the complete user-visible changes on the [https://www.octavegnu.org/downloadsoftware/octave/NEWS-3.8.html* [[Build From Source]NEWS file].
As of today, * Experimental GUI interface.* OpenGL graphics with fltk widgets.* Support for nested functions.* Support for java packages in Octave binaries are available at least on Debian, Ubuntu, RedHat, Suse core.* Reading and Fedora GNU/Linuxen, Mac OS X, Windows' 98, 2000 and XP, Vista, and 7writing of image files vastly extended.
==How do I get a copy What's new in version series 3.6.X of Octave for (some other platform)?==
Octave currently runs on UnixSee the complete user-like systems, Mac OS X, and Windows. It should be possible to make Octave work visible changes on other systems as well. If you are interested in porting Octave to other systems, please contact the [mailtohttps:maintainers@//www.gnu.org/software/octave/NEWS-3.6.org the maintainers' mailing listhtml NEWS file].
=Installation issues and problems= * Perl compatible regular expressions* A profiler has been added.* Broadcasting enabled for all built-in binary element-wise operators.* Performance of all m-file string functions has been improved.
Octave ==What's new in version series 3.4 requires approximately 1.3 GB X of disk storage to unpack and compile from source (considerably less if you don't compile with debugging symbols). Once installed, Octave requires approximately 355 MB of disk space (again, considerably less if you don't compile with debugging symbols, approximately 50 MB).==
==What else do I need?==See the complete user-visible changes on the [https://www.gnu.org/software/octave/NEWS-3.4.html NEWS file].
To compile * Many improvements to native OpenGL plotting* ARPACK now distributed with Octave, you will need * Indexing optimizations* FTP objects* Function handles aware of overloaded functions* bsxfun optimized for basic arithmetic functions* Matlab-style ignoring of output arguments using {{Codeline|~}}* Many optimizations of the accumarray function* Sparse matrix indexing has been rewritten for speed* The pkg command now accepts a recent version of GNU Make. You will also need GCC 4.3 or later, although GCC 4.4 or later is recommended.-forge option to pull packages directly from Octave Forge
'''You must have GNU Make to compile octave'''. Octave==What's Makefiles use features of GNU Make that are not present new in other versions of makeversion series 3. GNU Make is very portable and easy to install2.X of Octave==
==Can I compile Octave with another C++ compiler?==See the complete user-visible changes on the [https://www.gnu.org/software/octave/NEWS-3.2.html NEWS file].
Yes* Single precision type* Experimental OpenGL graphics toolkit to replace gnuplot* Object orient programming via @class named directories* 64-bit compilation support* gzipped files and stream and consequently support of Matlab v7 files* a fully compatible MEX interface* imwrite and imread (based on the GraphicsMagick library)* Lazy transpose: Special treatment in the parser of things like "a' * b", where the transpose is never explicitly formed but development a flag is done primarily with GCC, so you may hit some incompatibilities. Octave is intended to be portable to any standard conforming compiler. If you have difficulties that you think are bugs, please report them rather passed to the http://bugs.octave.org bug tracker, or ask for help on the [mailto:help@octave.org mailing list]underlying LAPACK code.
== How do I install ''all'' octave packages? Older releases==Do not do it! Really, there is no reason to do this. Octave Forge has many packages for different needs but it's unlikely that you need all of them. The common misconception is that the more packages one installs, the more complete and powerful its octave installation will be be. However, in the same way one would ''never'' install all perl modules, ruby gems or python packages (because it simply makes no sense), one should not install all octave packages. This isn't desirable and it's not even possible. Some packages conflict with each other, some are broken, others are just crappy and will break your system. What's worse, some packages are even loaded automatically at startup so you may be screwing your octave installation without even realizing it.
== Further links ==* Check the page [[Installation]] for more detailed information about installing Octave.For full details on older releases, see:
=Coding=* [http://hg.savannah.gnu.org/hgweb/octave/file/83792dd9bcc1/etc/NEWS.1 NEWS.1] for the 1.X.Y series* [http://hg.savannah.gnu.org/hgweb/octave/file/83792dd9bcc1/etc/NEWS.2 NEWS.2] for the 2.X.Y series* [http://hg.savannah.gnu.org/hgweb/octave/file/83792dd9bcc1/etc/NEWS.3 NEWS.3] for the 3.X.Y series
==What features are unique to Packages and Octave?=Forge=
Although most of the ==How do I install or load all Octave language will be familiar to Matlab users, it has some unique features of its own.Forge packages?==
=== Functions defined on the command-line===Functions can be defined by entering code on the command lineDo not do it! Really, there is no reason to do this. Octave has many packages for different needs and is unlikely that you need all of them. You either have a feature not supported small set of required packages, in which caseyou know them by Matlab. For examplename; or you want them all "just because", in which case you may type:don't really need them.
octave:1> function s = hello_string (to_who) > ## Say hello > if nargin<1The common misconception is that the more packages one has installed and loaded, the more complete and powerful its Octave installation will be. However, in the same way one would never install all perl modules, ruby gems, to_who = "World"; end > s = ["Hello "python packages,\ > to_who]; > endfunction octave:2> hello_string and C++ libraries ("Moon"because it simply makes no sense) ans = Hello Moon, one should not install all Octave packages.
As a natural extension of thisPackages should be installed and loaded selectively. Note that some packages are meant to shadow core functions changing the way Octave works, and that different packages can have different functions can also be defined in script files (m-files whose first non-comment line isn't {{Codeline|function out &#61; foo (..with the same name leading to unpredictable results.)}})
If you really really really want to do load all packages, you can with the following:<syntaxhighlight lang===Comments with "octave">##===WARNING: loading all packages is probably not the solution you are looking for.cellfun (@(x) pkg ("load", x.name), pkg ("list"));</syntaxhighlight>
The pound character, {{Codeline|#}}, may be used to start comments, in addition to {{Codeline|%}}. See the previous example. The major advantage of this is that as {{Codeline|#}} is also ==I have installed a comment character for unix script files, any file that starts with package but still get a string like {{Codeline|#! /usr/bin/octave -q}} will be treated as an octave script and be executed by octave."foo undefined" error?==
===Strings delimited You have probably forgotten to load the package. Use {{Codeline|pkg load package-name}} to load it. Most packages are no longer loaded automatically to avoid surprises. See reasoning on related FAQ [[FAQ#How_do_I_install_all_Octave_packages.3F|how do I install all Octave packages]]. If you want a specific package to be loaded by double quotes "===default at startup, consider adding the {{Codeline|pkg load}} command on your {{path|[[.octaverc]]}} file.
The double quote, {{Codeline|"}}, may be used to delimit strings, in addition to the single quote {{Codeline|'}}==I cannot install a package. See the previous example. Also, double-quoted strings include backslash interpretation (like C++, C, and Perl) while single quoted are uninterpreted (like Matlab and Perl)Octave complains about a missing mkoctfile.==
===Line continuation by backslash=== Lines can be continued with a backslash, {{Codeline|\}}, in addition to three points {{Codeline|...}}. See the previous example. ===Informative block closing=== You may close function, for, while, if, ..should normally use your distribution's packages. blocks with endfunction For Debian and Fedora, endfor, endwhile, ... keywords in addition to using end. As with Matlab, the end (Octave package <code>foo</code> will be a deb or endfunction) keyword that marks the end of a function defined in a .m file is optional. ===Coherent syntax=== Indexing other things than variables is possible, as in:  rpm called <code>octave:1-foo</code> [3 1 4 1 5 9](3) ans = 4 octave:2, and you should install that instead using <code> cos([0 pi piapt</4 7])(3) ans = 0.70711 In Matlab, it is for example necessary to assign the intermediate result {{Codeline|cos([0 pi picode> or <code>yum</4 7])}} to a variable before it can be indexed againcode>===Exclamation mark as not operator===
The exclamation mark If you really need to build Octave packages from source to install them, you'll need {{Codelinemanual|!mkoctfile}} (aka “Bang!”) is a negation operator, just like the tilde . Most distributions split Octave into several packages. The script {{Codelinemanual|~mkoctfile}}is then part of a separate package:
octave* Debian/Ubuntu:1> if ! strcmp (program_name, "octave"), > "It's an error" > else > "It works!" > end ans = It works!Note however that Matlab uses the {{Codeline|!}} operator for shell escapes, for which Octave requires using the system command[https://packages.debian.org/stretch/liboctave-dev liboctave-dev]
===Increment and decrement operators===* Fedora: {{Codeline|octave-devel}}
If you like the {{Codeline|++}}, {{Codeline|+&#61;}} etc operators, rejoice! ==How do I automatically load a package at Octave includes the C-like increment and decrement operators {{Codeline|++}} and {{Codeline|--}} in both their prefix and postfix forms, in addition to {{Codeline|+-}}, {{Codeline|-&#61;}}, {{Codeline|*&#61;}}, {{Codeline|/&#61;}}, {{Codeline|^&#61;}}, {{Codeline|.*&#61;}}, {{Codeline|./&#61;}}, and {{Codeline|.^&#61;}}.startup?==
For exampleWhen Octave starts, to pre-increment it runs the variable x, you would write file {{CodelinePath|++x}}. This would add one to x and then return the new value of x as the result of the expression~/. It is exactly the same as the expression {{Codeline|x &#61; x + 1octaverc}}(in your user's home directory)To post-increment a variable x, If you would write {{Codeline|x++}}. This adds one want Octave to the variable xautomatically load a package, but returns the value that x had prior simply add a <code>pkg load pkg-name</code> command to incrementing it. For example, if x is equal to 2, the result of If the expression x++ is 2files does not exist, and the new value of x is 3create it.
For matrix and vector argumentsIf you do this, remember that other people may not have Octave configured to load packages at startup. Therefore, if you write code for others, remember that your programs still need to load the increment and decrement operators work on each element of the operandpackages they require.
===Unwind-protect==Octave usage=
In addition to try-catch blocks, ==How do I execute an Octave supports an alternative form of exception handling modeled after the unwind-protect form of Lisp. The general form of an unwind_protect block looks like this:script?==
unwind_protect body unwind_protect_cleanup cleanup end_unwind_protectFirst of all, make sure you understand [http://www.octave.org/doc/interpreter/Script-Files.html the difference between script files and function files]. If you want to execute a function defined in a file, just call the function like any other Octave function: <code>foo(arg1, arg2);</code>
Where body and cleanup are both optional and may contain any To execute a script from within Octave expressions , just type its name without the <code>.m</code> extension. Thus, if you have a script called <code>foo.m</code>, just type <code>foo</code> from within the Octave command prompt to execute it. You have to make sure that the script is in your current working directory or commandsin Octave's load path. Type {{manual|pwd}} to get the current working directory or type {{manual|path}} to see which paths belong to Octave's load path. The statements current working directory is referred to as "." in cleanup are guaranteed to be executed regardless the output of how control exits body{{manual|path}}.
The unwind_protect statement is often used If the script name has characters that are not valid for an Octave identifier, or if you do not want to use {{manual|addpath}} to reliably restore add the values of global variables that need script's location to be temporarily changed.the current path, you can use the {{manual|run}} function instead:
Matlab can be made to do something similar with their {{Codeline|OnCleanUp}} function that was introduced in 2008a<syntaxhighlight lang="octave">run ("Script Name With Spaces. Octave also has {{Codeline|onCleanup}} since version 3.4.0m")run ("/opt/local/foo.m")</syntaxhighlight>
===Built-in ODE and DAE solvers===An alternative is to run the script from outside Octave by calling Octave from your operating system shell. Unlike calling the script from inside Octave, this also allows you to pass arguments from the shell into the script, which the script can access using the {{manual|argv}} command:
Octave includes LSODE and DASSL for solving systems of stiff ordinary differential and differential $octave the-algebraic equations. These functions are built in to the interpreterscript.m arg1 arg2 ==How does Octave solve linear systems?==In a Unix environment, if the script has a [http://en.wikipedia.org/wiki/Shebang_%28Unix%29 shebang] (e.g. <code>#!/usr/bin/octave</code>) and executable permissions, you can call it like any other Unix program with arguments: In addition to consulting Octave's source for the precise details, you can read the Octave manual for a complete high-level description of the algorithm that Octave uses to decide how to solve a particular linear system, e$ .g. how /the backslash operator {{Codeline|A\x}} will be interpreted. Sections [http://www.gnu.org/software/octave/doc/interpreter/Techniques-Used-for-Linear-Algebra.html#Techniques-Used-for-Linear-Algebra Techniques Used for Linear Algebra] and [http://www.gnu.org/software/octave/doc/interpreter/Sparse-Linear-Algebra.html Linear Algebra on Sparse Matrices] from the manual describe this procedure.script arg1 arg2
=How do If you call the script from the shell and it's plotting, please note [[#When Itry plotting from a script, why am I not seeing anything?|how to plot when running a script from the shell]]...?=
==How do xxxxI close a figure?==
You are probably looking for To close the function ''lookfor''. This function searches the help text of all functions for a specific string and returns a list of functions. Note that by default it will only search current figure type {{manual|close}} in the first line of the help text (check ''help lookfor'' at the octave Octave command prompt for more). The following example helps to find the function to calculate correlation coefficient in a matrix:  octave:1> lookfor ("correlation") corr2 Returns the correlation coefficient between I and J. cor Compute correlation. corrcoef Compute correlation. spearman Compute Spearman's rank correlation coefficient RHO for each of the variables sp autocor Return the autocorrelations from lag 0 to H of vector XAlso, there's a high chance that the function name has a suggestive name, and so you can try auto-completion to get some hints. For the previous example, typing ''corr'' at the octave promp followed by pressing [Tab] twice would suggest the following:  octave:2> corr corr2 corrcoef ==How do I erase a figure?==   closeplot(); closefig(number)
==How do I set the number of displayed decimals?==
octave:1> format long octave:2> pi pi = 3.14159265358979 octave:3> format short octave:4> pi pi = 3.1416 ==How do I vary the line thickness?== * There's plpot_octave, but the one in debian doesn't work for me.* Here's my octave hack for it--- http://gnufans.net/~deego/pub/octave/plot_width.m This one simply draws the line multiple times.* You can edit control the .eps file manually or number of displayed decimals using sed and awk.* Export the graph as fig file (gset term fig thickness 2). This also allows for easy postediting with xfig and export to formats not supported by gnuplot.* The gplot {{manual|format}} command of octave does not support gnuplot's linewidth parameter Thus you must use the graw() function for sending this option directly to gnuplot, eg. graw('replot "" notitle with lines lw 4\n');*Search the [http://octave.1599824.n4.nabble.com/ octave archives] for more. ==How do I call an octave function from C++?== *Here is an untested code snippet for calling rand([9000,1]), modified from a post by HerberFarnsworth? to help-octave on 2003-05-01:
#include <syntaxhighlight lang="octave/oct.h"> ...>> format long ColumnVector NumRands(2);>> pi NumRands(0) pi = 9000;3.14159265358979 NumRands(1) = 1;>> format short octave_value_list f_arg, f_ret;>> pi f_arg(0) pi = octave_value(NumRands);3.1416 f_ret = feval("rand",f_arg,1); Matrix unis(f_ret(0).matrix_value());</syntaxhighlight>
==How do I create a full semilog/log gridcall an Octave function from C++?==
gset grid mxtics mytics gset grid lw 2, lw 0Please read the manual https://www.gnu.org/software/octave/doc/interpreter/Calling-Octave-Functions-from-Oct_002dFiles.html.1 grid("on");
One can use ==How do I change color/line definition in gnuplot postscript enhancement for proper axis gset format x "10^{%%L}"or gset format y "10^{%%L}" ?==
==How do I change colour/line definition in gnuplot postscript?==Here is a awk script to get a rainbow colour color map
#!/bin/awk -f
==How do I tell if a file exists?==
==How do I do X?==
==How do I create You are probably looking for the function {{manual|lookfor}}. This function searches the help text of all functions for a plot without specific string and returns a window popping up list of functions. Note that by default it will only search the first line of the help text (ie, a plot check <code>help lookfor</code> at the octave prompt for more). The following example helps to find the function to calculate correlation coefficient in a file)?==matrix:
figure(1, "visible", "off");>> lookfor correlation plot(sin(1:100));corr Compute matrix of correlation coefficients. corrcoef Compute a matrix of correlation coefficients. print -deps "/tmp/sinspearman Compute Spearman's rank correlation coefficient RHO.eps"
One Also, there's a high chance that the function name has a suggestive name, and so you can set that behaviour as defaulttry auto-completion to get some hints. For the previous example, typing <code>corr</code> at the octave prompt followed by pressing the {{key press|Tab}}-Key twice would suggest the following:
set(0, 'defaultfigurevisible', 'off');>> corr corr corrcoef
=Common problems=

==I do not see any output of my script until it has finished?==

By default Octave is set to pass its screen output through a [https://en.wikipedia.org/wiki/Terminal_pager pager] (usually the default pager is "less") which allows things such as navigating through the output with arrow keys or searching for text or regular expressions within the output. The pager only displays the output after it's finished receiving it, so when it is active you'll not be able to see anything until your script has terminated. To change this behavior temporarily or permanently you may want to use one of the options described [http://www.octave.org/doc/interpreter/Paging-Screen-Output.html in the manual].
==When I try plotting from a script, why am I not seeing anything?==
If you are running an Octave script that includes a plotting command, the script and Octave may terminate immediately. So the plot window does show up, but immediately closes when Octave finishes execution. Alternatively, if using fltk, the plot window needs a readline loop to show up (the time when Octave is sitting around doing nothing waiting for interactive input). A common solution is to put a {{manual|pause}} command at the end of your script. ==How do I get sound input or output in Windows?== Sound input from a sound card and output to a sound card is fully supported since Octave 4.0.0 for all platforms. If you have problems with the [http://www.octave.org/doc/interpreter/Audio-Processing.html audio I/O functions] using Octave 4.0.0 or a newer version, please report them on the [http://bugs.octave.org bug tracker]. ==I have problem X using the latest Octave version==
==How do I get sound output in Windows?== See http://www* The latest stable version is {{Release}}.octave Be aware that you may still have an older version due to whatever distribution method you are using.org To get a newer stable version for your system see for example [[Octave for GNU/octave-listsLinux|GNU/archive/help-octave.2003/msg01567.html Linux]], [[Octave for macOS|macOS]], or [[Octave for a startMicrosoft Windows|Windows]]).
==Why does Octave segfault when using "clear * If you refer to the latest Mercurial revision, please specify the [https://www.mercurial-scm.org/wiki/ChangeSetID changeset ID] not the revision number, e.g. the output of <code>hg summary</code> or <code>hg id</code>. Changeset IDs are globally unique across all;"?==repos.
This is If your problem truly persists with the "latest version", then please [http://bugs.octave.org/ report a known problem bug] or ask for help at[https://lists.gnu.org/mailman/listinfo/help-octave help@octave.org]. Otherwise, don't be surprised if volunteers are less inclined to help you have one with a problem that only exists in an older version of the following packages loaded:Octave and is already fixed in a newer version.
* ann* database* ftp ==Why is Octave's floating-point computation wrong?==
See http:Floating-point arithmetic is an approximation '''in binary''' to arithmetic on real or complex numbers. Just like you cannot represent 1/3 exactly in decimal arithmetic (0.333333... is only a rough approximation to 1/www3), you cannot represent some fractions like $1/10$ exactly in base 2. In binary, the representation to one tenth is $0.nabble0\overline{0011}_b$ where the bar indicates that it repeats infinitely (like how [itex]1/6 = 0.com1\overline{6}_d</Segmentationmath> in decimal). Because this infinite repetition cannot be represented exactly with a finite number of digits, rounding errors occur for values that appear to be exact in decimal but are in fact approximations in binary, such as for example how 0.3 -Fault0.2 ---Clear-all-td219985630.1 is not equal to zero.html for a discussion
==Octave takes a long time In addition, some advanced operations are computed by approximation and are not guaranteed to find symbolsbe accurate, see [https://en.wikipedia.org/wiki/Rounding#Table-maker.27s_dilemma Table-maker's dilemma]. Their results are system-dependent.==
This isn't an Octave bug. It happens with any program that uses the genpath function to recursively add directories to the list of directories searched for function files[https://en.wikipedia.org/wiki/IEEE_754 IEEE 754 floating-point arithmetic]. Check the list of directories with the path command To be fair, IEEE 754 also specifies decimal floating-point arithmetic, which has never seen wide adoption. If the path list The reason why Octave and other programs using IEEE 754 binary floating-point numbers is that they are ''fast'', because they are implemented in hardware or system libraries. Unless you are using very long check exotic hardware, Octave will use your use of the genpath functioncomputer's processor for basic floating-point arithmetic.
==When plotting Octave occasionally gives me Another approach to deal with rounding errors like <tt>gnuplot> 9 0.735604 line 26317: invalid command</tt>.==There is a known bug in gnuplot 4interval arithmetic with the [[Interval package]] or symbolic computatons with the [[Symbolic package]].2 that These approaches are likely to be slower, since not all operations can cause an off by one error while piping data to gnuplot. It has been fixed in gnuplot 4.4be performed on Hardware like pure floatin-point arithmetic.
If you have obtained your copy of Octave from a distribution please file a bug report requesting that To learn more about floating-point arithmetic, consult the fix reported in [https://en.wikipedia.org/wiki/Floating-point_arithmetic Wikipedia article] or the above bug report be includedclassical reference by David Goldberg [http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html What Every Computer Scientist Should Know About Floating-Point Arithmetic].
==I cannot install a package. Octave complains about a missing mkoctfile.Missing lines when printing under Windows with OpenGL toolkit and Intel integrated GPU==
Most distributions split Octave into several packagesSome windows users with integrated Intel GPUs have reported missing lines when printing with an OpenGL toolkit like FLTK or Qt. The script mkoctfile is then part of a separate package:{{bug|42534}}
* DebianUsers with this kind of problem should try to install/Ubuntu<brupdate their Intel OpenGL drivers for Windows or consider installing Mesa drivers from http:/> aptitude install octave/qt-project.org/wiki/Cross-compiling-Mesa-for-headersWindows .
== I'm having problem XXX using Plot hangs and makes the latest Octave version GUI unresponsive==
Please be more specific. What If the Qt graphics toolkit is used and "plot" is used for the latest versionfirst time, according to you? If you mean the latest released version, be aware that you may still have an older version due to whatever distribution method you're using. There may be a newer version available that you're not aware of due to fontconfig scanner searches the distribution method you're using font directory to get Octave, and in most cases, there is build a way font cache. This can take up to get a newer version via your distribution method3min on slow CPUs.See {{bug|45458}}
If you mean the latest Mercurial revision, please specify which one that is. "Latest tip" is not informative, because from the time you wrote "latest tip" ==Error message about invalid call to the time someone reads that message, "latest tip" might have changed meaning. Instead, report the output of "hg summary" script or "hg id". Also please invalid use hash numbers instead of revision numbers. Revision numbers are just a convenience and only make sense script in your local repo, and might not coincide with what someone sees on their own repo. Hashes are globally unique across all repos.index expression==
If your problem truly persists with the latest revision, as indicated [http:Octave shows an error message about {{Codeline|invalid call to script ...//wwwclose.m}} or {{Codeline|invalid use of of script ..gnu.org/software/octave/downloadclose.html here]m in index expression}}, then by all it means report a bug or ask for help, but don't be surprised if volunteers are less inclined to help that you with have created a problem script called close.m that only exists is overriding the built-in Octave function {{Codeline|close}}. Octave functions and scripts share the samem global namespace. It is best to avoid creating your own scripts or functions that have the same name as an older version of Octavefunction.
=Porting programs from Differences between Octave and Matlab to Octave=
<blockquote>
I wrote some code for Matlab, and I want to get it running under Octave. Is there anything I should watch out for?
</blockquote>
<blockquote>
I wrote some code in Octave, and want to share it with Matlab users. Is there anything I should watch out for?
</blockquote>
which is not quite the same thing. There are still a number of differences between Octave and Matlab, however in general differences between the two are considered as bugs. Octave might consider that the bug is in Matlab and do nothing about it, but generally functionality is almost identical. If you find a an important functional difference between Octave behavior and Matlab, then you should send a description of this difference (with code illustrating the difference, if possible) to http://bugs.octave.org.
Furthermore, Octave adds a few syntactical extensions to Matlab that might cause some issues when exchanging files between Matlab and Octave users. As both Octave and Matlab are under constant development the information in this section is subject to change at anytime.
You should also look at As both Octave and Matlab are under constant development, the page http://octave.sourceforge.net/packages.html and http://octave.sourceforge.net/doc/ that has a function reference that information in this section is up subject to date. You can use this function reference to see the number of octave function that are available and their Matlab compatibilitychange.
==How You should also look at the pages http://octave.sourceforge.net/packages.php and http://octave.sourceforge.net/docs.html that have a function reference that is Octave different from up to date. You can use this function reference to see the number of octave functions that are available and their Matlab?==compatibility.
The major differences between Octave 3.4.N and Matlab R2010b are:==Nested Functions==
===Nested Functions===Octave has limited support for nested functionssince version 3.8.0. That is
<syntaxhighlight lang="Matlab">function y = foo (x) y = bar(x) function y = bar (x) y = ...; end end</syntaxhighlight>
is equivalent to
<syntaxhighlight lang="Octave">function y = foo (x) y = bar(x) endendfunction  function y = bar (x) y = ...; endendfunction</syntaxhighlight>
The main difference with Matlab is a matter of scope. While nested functions have access to the parent function's scope in Matlab, no such thing is available in Octave, due to how Octave essentially “un-nests” nested functions.
The authors of Octave consider the nested function scoping rules of Matlab to be more problems than they are worth as they introduce difficult to find bugs as inadvertently modifying a variable in a nested function that is also used in the parent is particularly easy for those not attentive to detail.
===Differences in core syntax===
There are a few core Matlab syntaxes that are not accepted by Octave, these being
* Some limitations on the use of function handles. The major difference is related to nested function scoping rules (as above) and their use with function handles.
* Some limitations of variable argument lists on the LHS of an expression, though the most common types are accepted.
* Matlab classdef object oriented programming is not yet only partially supported, though work is underway and when development moves on to Octave 3.5 this will be included in the development treesee [[classdef]] for details.
===Differences in core functions===
A large number of the Matlab core functions (ie i.e. those that are in the core and not a toolbox) are implemented, and certainly all of the commonly used ones. There are a few functions that aren't implemented, usually to do with specific missing Octave functionality (GUI, DLL, Java, ActiveX, DDE, web, and serial functions). Some of the core functions have limitations that aren't in the Matlab version. For example the {{manual|sprandn }} function can not force a particular condition number for the matrix like Matlab can. Another example is that testing and the runtests function work differently in Matlab and Octave.
===Just-In-Time compiler===
Matlab includes a "Just-In-Time" compiler. This compiler allows the acceleration of for-loops in Matlab to almost native performance with certain restrictions. The JIT must know the return type of all functions called in the loops and so you can't include user functions in the loop of JIT optimized loops. Octave doesn't have has a [[JIT|not fully functional JIT and so to some might seem slower than Matlabcompiler]]. For this reason you must [[Performance#Vectorization|vectorize your code ]] as much as possible. The MathWorks themselves have a good document discussing vectorization at http://www.mathworks.com/support/tech-notes/1100/1109.html.
===Compiler===
On a related point, there is no Octave compiler, and so you can't convert your Octave code into a binary for additional speed or distribution. There have been several aborted attempts at creating an Octave compiler. Should the JIT compiler above ever be implemented, an Octave compiler should be more feasible.
===Graphic handles===
Up to Octave 2.9.9 there was no support for graphic handles in Octave itself. In the 3.2.N versions of Octave and beyond the The support for graphics handles is converging towards full compatibility. The patch function is currently limited to 2-D patches If you notice any incompatibilities, due to an underlying limitation in gnuplot, but the experimental OpenGL backend is starting to see an implementation of 3-D patchesplease [http://bugs.octave.org report a bug].
===GUI functions ===
There are no The support for [http://www.octave.org/doc/interpreter/GUI-Development.html Matlab compatible GUI functions yet] was added in Octave version 3.6.0 and is converging towards full compatibility. This might be an issue if If you intend to exchange Octave code with Matlab users. There are a number of bindings from Octave to {{Forge|tcl-octave|Tcl/Tk}}notice any incompatibilities, please [http://octavizbugs.sourceforgeoctave.net/index.php? VTKorg report a bug] and {{Forge|zenity}} for example, that can be used for a GUI, but these are not Matlab compatible. Work on a Matlab compatible GUI is in an alpha stage in the QtHandles project, which may form part of a future release of Octave.
Octave itself includes no Simulink support. Typically the simulink models lag research and are less flexible, so shouldn't really be used in a research environment. However, some Matlab users that try to use Octave complain about this lack.
===MEX-Files===
Octave includes an [http://www.octave.org/doc/interpreter/Mex_002dFiles.html API to the Matlab MEX interface]. However, as MEX is an API to the internals of Matlab and the internals of Octave differ from Matlab, there is necessarily a manipulation of the data to convert from a MEX interface to the Octave equivalent. This is notable for all complex matrices, where Matlab stores complex arrays as real and imaginary parts, whereas Octave respects the C99/C++ standards of co-locating the real/imag parts in memory. Also due to the way Matlab allows access to the arrays passed through a pointer, the MEX interface might require copies of arrays (even non complex ones).
Block comments denoted by {{Codeline|<code>#{}} </code> and {{Codeline|<code>#&#125;}} </code> markers (or {{Codeline| <code>%{}} </code> and {{Codeline|<code>%&#125;}}</code>) are supported by Octave with some limitations. The major limitation is that block comments are not supported within [] or {}.
===Mat-File format===
There are some differences in the mat v5 file format accepted by Octave. Matlab recently introduced the "-V7.3" save option which is an HDF5 format which is particularly useful for 64-bit platforms where the standard Matlab format can not correctly save variables. Octave accepts HDF5 files, but is not yet compatible with the "-v7.3" versions produced by Matlab.
Although Octave can load inline function handles saved by Matlab, it can not yet save them.
Finally, Some some multi-byte Unicode characters aren't yet treated in mat-files.
===Profiler===
Thanks to Daniel Kraft's 2011 Google Summer of Code project, [http://www.octave.org/doc/interpreter/Profiling.html Octave has a profiler ] since version 3.6.0. However, at the moment it only produces text output and has its own makeshift interface for hierarchical profiling.
===Toolboxes===
Octave is a community project and so the toolboxes that exist are donated by those interested in them through [http://octave.sourceforge.net [Octave Forge]]. These might be lacking in certain functionality relative to the Matlab toolboxes, and might not exactly duplicate the Matlab functionality or interface.
===Short-circuit {{Codeline|<code>&}} </code> and {{Codeline<code>|&#124;}} </code> operators===
The {{Codeline|<code>&}} </code> and {{Codeline<code>|&#124;}} </code> operators in Matlab short-circuit when included in a condition (e.g. an {{Codeline|if}} or {{Codeline|while}} statement) and not otherwise. In Octave only the {{Codeline|<code>&&}} </code> and {{Codeline<code>||&#124;&#124;}} </code> short circuit. Note that this means that
<syntaxhighlight lang="Octave">if (a | b) ... end</syntaxhighlight>
and
<syntaxhighlight lang="Octave">t = a | b; if (t) ... end</syntaxhighlight> have different semantics in Matlab. This is really a Matlab bug, but there is too much code out there that relies on this behavior to change it. Prefer the <code>&&</code> and <code>||</code> operators in {{Codeline|if}} statements if possible.
have different semantics in Note that the difference with Matlab. This is really also significant when either argument is a Matlab bug, but there function with side effects or if the first argument is too much code out there that relies on this behaviour to change it. Prefer a scalar and the {{Codeline|&#124;&#124;}} and {{Codeline|&&}} operators in {{Codeline|if}} statements if possiblesecond argument is an empty matrix. If you need to use code written for Matlab that depends on this buggy behaviour For example, you can enable it since Octave 3.4.0 with note the following command:difference between
do_braindead_shortcircuit_evaluation<syntaxhighlight lang="Octave">t = 1 | []; ## results in [], so...if (t) 1, end ## in if ([]), this is false.</syntaxhighlight>
Note that the difference with Matlab is also significant when either argument is a function with side effects or if the first argument is a scalar and the second argument is an empty matrix. For example, note the difference between
t <syntaxhighlight lang= "Octave">if (1 | []; ## results in [], so... if (t) 1, end ## in if ([]), this short circuits so condition is falsetrue.</syntaxhighlight>
andIn the latter case, Octave displays since version 4.0.0 a warning:
if (1 | []) 1, end ## warning: Matlab-style short circuits so condition is true.-circuit operation performed for operator |
Another case that is documented in the Matlab manuals is that
<syntaxhighlight lang="Matlab">t = [1, 1] | [1, 2, 3]; ## error if ([1, 1] | [1, 2, 3]) 1, end ## OK</syntaxhighlight>
Also Matlab requires the operands of {{Codeline|<code>&&}} </code> and {{Codeline<code>||&#124;&#124;}} </code> to be scalar values but Octave does not (it just applies the rule that for an operand to be considered true, every element of the object must be nonzero or logically true).
Finally, note the inconsistence of thinking of the condition of an {{Codeline|if}} statement as being equivalent to {{Codeline|all(X(:))}} when {{Codeline|X}} is a matrix. This is true for all cases EXCEPT empty matrices:
<syntaxhighlight lang="Matlab">if ([0, 1]) == if (all ([0, 1])) ==> i.e., condition is false. if ([1, 1]) == if (all ([1, 1])) ==> i.e., condition is true.</syntaxhighlight>
However,
<syntaxhighlight lang="Matlab">if ([])</syntaxhighlight>
is not the same as
<syntaxhighlight lang="Matlab">if (all ([]))</syntaxhighlight>
because, despite the name, the {{Codelinemanual|all}} is really returning true if none of the elements of the matrix are zero, and since there are no elements, well, none of them are zero. This is an example of [httphttps://en.wikipedia.org/wiki/Vacuous_truth vacuous truth]. But, somewhere along the line, someone decided that {{Codeline|if ([])}} should be false. The Mathworks probably thought it just looks wrong to have {{Codeline|[]}} be true in this context even if you can use logical gymnastics to convince yourself that "all" the elements of an empty matrix are nonzero. Octave however duplicates this behavior for {{Codeline|if}} statements containing empty matrices.
===Solvers for singular, under- and over-determined matrices===
Matlab's solvers as used by the operators {{manual|mldivide (}} <code>\) </code> and {{manual|mrdivide (}} <code>/</)code>, use a different approach than Octave's in the case of singular, under-, or over-determined matrices. In the case of a singular matrix, Matlab returns the result given by the LU decomposition, even though the underlying solver has flagged the result as erroneous. Octave has made the choice of falling back to a minimum norm solution of matrices that have been flagged as singular which arguably is a better result for these cases.
In the case of under- or over-determined matrices, Octave continues to use a minimum norm solution, whereas Matlab uses an approach that is equivalent to
<syntaxhighlight lang="Octave">function x = mldivide (A, b) m = rows(A); [Q, R, E] = qr(A); x = [A \ b, E(:, 1:m) * (R(:, 1:m) \ (Q' * b))] end</syntaxhighlight>
While this approach is certainly faster and uses less memory than Octave's minimum norm approach, this approach seems to be inferior in other ways.
A numerical question arises: how big can the null space component become, relative to the minimum-norm solution? Can it be nicely bounded, or can it be arbitrarily big? Consider this example:
<syntaxhighlight lang="Octave">m = 10; n = 10000; A = ones(m, n) + 1e-6 * randn(m,n); b = ones(m, 1) + 1e-6 * randn(m,1); norm(A \ b)</syntaxhighlight>
while Octave's minimum-norm values are around about 3e-2, Matlab's results are 50-times larger. For another issue, try this code:
<syntaxhighlight lang="Octave">m = 5; n = 100; j = floor(m * rand(1, n)) + 1; b = ones(m, 1); A = zeros(m, n); A(sub2ind(size(A),j,1:n)) = 1; x = A \ b; [dummy~,p] = sort(rand(1,n)); y = A(:,p)\b; norm(x(p)-y)</syntaxhighlight>
It shows that unlike in Octave, {{manual|mldivide }} in Matlab is not invariant with respect to column permutations. If there are multiple columns of the same norm, permuting columns of the matrix gets you different result than permuting the solution vector. This will surprise many users.
Since the {{manual|mldivide (}} <code>\) </code> and {{manual|mrdivide (}} <code>/</) code> operators are often part of a more complex expression, where there is no room to react to warnings or flags, it should prefer intelligence (robustness) to speed, and so the Octave developers are firmly of the opinion that Octave's approach for singular, under- and over-determined matrices is a better choice than Matlab's.
===Octave extensions===
The extensions in Octave over Matlab MATLAB syntax are very useful, but might cause issues when sharing with Matlab users. A list of the major extensions that should be avoided to be compatible with Matlab are:
Comments in octave Octave can be marked with {{Codeline|#}}. This allows POSIX systems to have the first line as {{Codeline|#! octave -q}} and mark the script itself executable. Matlab MATLAB doesn't have this feature due to the absence of comments starting with {{Codeline|#}}".
Code blocks like if, for, while, etc can be terminated with block specific terminations like endif. Matlab MATLAB doesn't have this and all blocks must be terminated with end.
Octave has a lisp-like {{Codeline|unwind_protect}} block that allows blocks of code that terminate in an error to ensure that the variables that are touched are restored. You can do something similar with try/catch combined with {{Codeline|rethrow (lasterror ())}} in Matlab, however rethrow and lasterror are only available in Octave 2.9.10 and later. Matlab MATLAB 2008a also introduced {{Codeline|OnCleanUp}} that is similar to {{Codeline|unwind_protect}}, except that the object created by this function has to be explicitly cleared in order for the cleanup code to run.
Note that using try/catch combined with {{Codeline|rethrow (lasterror ())}} can not cannot guarantee that global variables will be correctly reset, as it won't catch user interrupts with Ctrl-C. For example
<syntaxhighlight lang="Matlab">global a a = 1; try _a = a; a = 2 while true end catch fprintf ('caught interrupt\n'); a = _a; rethrow (lasterror()); end</syntaxhighlight>
compared to
<syntaxhighlight lang="Octave">global a a = 1; unwind_protect _a = a; a = 2 while true end unwind_protect_cleanup fprintf ('caught interrupt\n'); a = _a; end</syntaxhighlight>
Typing Ctrl-C in the first case returns the user directly to the prompt, and the variable ''<code>a'' </code> is not reset to the saved value. In the second case the variable ''<code>a'' </code> is reset correctly. Therefore Matlab gives no safe way of temporarily changing global variables.
Indexing can be applied to all objects in Octave and not just variables. Therefore {{Codeline|sin(x)(1:10)}} for example is perfectly valid in Octave but not Matlab. To do the same in Matlab you must do {{Codeline|y &#61; sin(x); y &#61; y([1:10]);}}
Octave has the operators {{Codeline|++}}, {{Codeline|–-}}, {{Codeline|-&#61;}}, {{Codeline|+&#61;}}, {{Codeline|*&#61;}}, etc. As Matlab MATLAB doesn't, if you are sharing code these should be avoided. Character strings in Octave can be denoted with double or single quotes. There is a subtle difference between the two in that escaped characters like {{Codeline|\n}} (newline), {{Codeline|\t}} (tab), etc are interpreted in double quoted strings but not single quoted strings. This difference is important on Windows platforms where the {{Codeline|\}} character is used in path names, and so single quoted strings should be used in paths. MATLAB doesn't have double quoted strings and so they should be avoided if the code will be transferred to a MATLAB user. ==What features are unique to Octave?== Although most of the Octave language will be familiar to Matlab users, it has some unique features of its own. === Functions defined on the command-line===Functions can be defined by entering code on the command line, a feature not supported by Matlab. For example, you may type: <syntaxhighlight lang="Octave">>> function s = hello_string (to_who)> ## Say hello> if nargin<1, to_who = "World"; end> s = ["Hello ",\> to_who];> endfunction>> hello_string ("Moon")ans = Hello Moon</syntaxhighlight> As a natural extension of this, functions can also be defined in script files (m-files whose first non-comment line isn't {{Codeline|function out &#61; foo (...)}}) Note: MATLAB R2016b added the ability to [http://www.mathworks.com/help/matlab/matlab_prog/local-functions-in-scripts.html define functions in script files]. ===Comments with #=== The pound character, {{Codeline|#}}, may be used to start comments, in addition to {{Codeline|%}}. See the previous example. The major advantage of this is that as {{Codeline|#}} is also a comment character for unix script files, any file that starts with a string like {{Codeline|#! /usr/bin/octave -q}} will be treated as an octave script and be executed by octave. ===Strings delimited by double quotes "=== In 2016, Matlab introduced String Arrays, that are initialized by using double quoted strings, and are not implemented in Octave yet. In Octave double-quoted strings include backslash interpretation (like C++, C, and Perl) while single quoted are uninterpreted (like Matlab and Perl). ===Line continuation by backslash=== Lines can be continued with a backslash, {{Codeline|\}}, in addition to three points {{Codeline|...}} as in Matlab. ===Informative block closing=== You may close function, for, while, if, ... blocks with endfunction, endfor, endwhile, ... keywords in addition to using end. As with Matlab, the end (or endfunction) keyword that marks the end of a function defined in a .m file is optional. ===Coherent syntax=== Indexing other things than variables is possible, as in: <syntaxhighlight lang="Octave">>> [3 1 4 1 5 9](3)ans = 4>> cos([0 pi pi/4 7])(3)ans = 0.70711</syntaxhighlight> In Matlab, it is for example necessary to assign the intermediate result {{Codeline|cos([0 pi pi/4 7])}} to a variable before it can be indexed again. ===Exclamation mark as not operator=== The exclamation mark {{Codeline|!}} (aka “Bang!”) is a negation operator, just like the tilde {{Codeline|~}}: <syntaxhighlight lang="Octave">>> if ! strcmp (program_name, "octave"),> "It's an error"> else> "It works!"> endans = It works!</syntaxhighlight>
Character strings in Octave can be denoted with double or single quotes. There is a subtle difference between the two in Note however that escaped characters like {{Codeline|\n}} (newline), {{Codeline|\t}} (tab), etc are interpreted in double quoted strings but not single quoted strings. This difference is important on Windows platforms where Matlab uses the {{Codeline|\!}} character is used in path namesoperator for shell escapes, and so single quoted strings should be used in paths. Matlab doesn't have double quoted strings and so they should be avoided if for which Octave requires using the code will be transferred to a Matlab usersystem command.
=GUI=This is a small section but it's probably one of the most frequent questions.=Increment and decrement operators===
==Is there a GUI for If you like the {{Codeline|++}}, {{Codeline|+&#61;}} etc operators, rejoice! Octave?==Noincludes the C-like increment and decrement operators {{Codeline|++}} and {{Codeline|--}} in both their prefix and postfix forms, in addition to {{Codeline|+&#61;}}, {{Codeline|-&#61;}}, {{Codeline|*&#61;}}, {{Codeline|/&#61;}}, {{Codeline|^&#61;}},{{Codeline|.+&#61;}},{{Codeline|.-&#61;}},{{Codeline|.*&#61;}}, {{Codeline|./&#61;}} and {{Codeline|.^&#61;}}.
==Is there a GUI planned for Octave?==YesFor example, and is already in development. You can download to pre-increment the [http://wwwvariable x, you would write {{Codeline|++x}}.gnu.org/software/octave/get-involved.html Octave repository] This would add one to x and compile then return the new value of x as the development branch yourself (it seems to be stable enough for use and result of the 3.6.2 binaries for windows already have it). Testing is always welcomed, and patches even more. Note that despite being called Octave GUI, it is ''not'' a separate projectexpression. It is simply exactly the ''Octave GUI'', same as the Octave Graphical User Interface, just like the Octave prompt, Octave interpreter, etc are not separate projects (not to be confused with the completely unrelated but similarly named, GUI Octave project)expression {{Codeline|x &#61; x + 1}}.
==How come there's still no GUI for Octave?==The Octave prompt is really really good and that's what To post-increment a variable x, you would write {{Codeline|x++}}. This adds one to the Octave developers use. Octave is community project which means that it has variable x, but returns the functionalities value that its users are willing x had prior to spend time implementingincrementing it. Since Octave developers do not need a GUI (some actually would not use one For example, if it existed), they have no reason x is equal to make one. Also2, many people on the community are result of the opinion that using a GUI slows down expression x++ is 2, and the learning new value of the languagex is 3.
==I want Octave developers to work on a GUI?==If you would like the Octave developers to implement a GUI for youFor matrix and vector arguments, consider the same route taken by others that want a specific function/capability to be implemented. Some of the Octave developers will increment and decrement operators work as coders for hire. Ask on each element of the [http://www.gnu.org/software/octave/get-involved.html maintainers mailing list]. This is not unlike paying a builder to add an extra room to your house. The fact there is no GUI in Octave only shows that there is not enough interest for it (despite the amount of time people asking for it)operand.
==What about all the Octave GUIs I find on Google?=Unwind-protect===None of the GUIs for Octave that have been developed thus far are part of Octave and there is a reason for it. All of them fail at a very important point, integration with Octave. They treat Octave as a foreign black box using pipes for communication, an approach that is bound to eventually fail. This includes QtOctave (now abandoned and incompatible with newer versions of Octave), Xoctave (which is proprietary and commercial) and GUI Octave (which is proprietary and the author is not interested to share his code to preserve its "artistic integrity").