FAQ: Difference between revisions

* Contact our user community using our [https://octave.discourse.group Octave Discourse].

The GNU Octave language is quite similar to Matlab so that most programs are easily portable.

==What is Octave Forge?==

[https://octave.sourceforge.io/ 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).

A huge number of people ranging from students to researchers involved in various fields such as statistics, Machine Learning, data analytics, etc. Universities use it for research and teaching, companies of all sizes for development and individuals for certain private purposes. See [[Who Uses Octave?]] for more clarity.

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 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). Since 2011, GNU Octave regularly  participates in [[Summer of Code]] events as a mentor organisation. As part of those events, several students contributed to Octave by helping in removal of bugs and development of new features.

The [https://www.fsf.org/ Free Software Foundation (FSF)] is the principal organization that has sponsored the GNU Project.

   John W. Eaton, David Bateman, Søren Hauberg, Rik Wehbring ({{Release Year}}).

   URL https://octave.org/doc/v{{Release}}/

     year      = <span>{</span>{{Release Year}}},

     url      = {[https://octave.org/doc/v{{Release}}/ https://octave.org/doc/v{{Release}}/]},

Run {{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>.

Note that there are two reasons for citing the software used.  One is giving recognition to the work done by others which we have already addressed to. The other is giving details on the system used so that experiments can be replicated.  For this, you should cite the version of Octave and all packages used (you can get this information using the <code>ver</code> command), as well as any details of your setup as part of your Methods.  In addition, you should make your source available as well. See [http://software.ac.uk/so-exactly-what-software-did-you-use How to cite and describe software] for more details and an in depth discussion for the same.

Besides this wiki, the GNU Octave distribution includes a [http://www.octave.org/doc/interpreter 1000+ page Texinfo manual] ([http://www.octave.org/octave.pdf PDF]).  Access to the complete text of the manual is available via the {{manual|doc}} command at the GNU Octave prompt.  If you have problems using this manual, or find that some topic is not adequately explained, indexed, or cross-referenced, please report it on http://bugs.octave.org.

:# The MEX file 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 to effectively create a single work.

'''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, this way the free software community can be benefited from your work the same as you were/have benefited from the work of all the people who have contributed to Octave.

'''No.''' 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 free softwares 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 [https://www.gnu.org/licenses/gpl.html GPL].

:'' So as to install GNU-Octave for Windows O.S, refer to : [[Octave for Microsoft Windows]]''

==How can I install Octave on MacOS?==

:''So as to install GNU-Octave for MacOS, refer to : [[Octave for macOS]]''

:'' So as to install GNU-Octave on GNU/Linux, refer to: [[Octave for GNU/Linux]]''

==How to install Octave on Android OR What is the Octave app available in the Google Play store?==

There is an '''unofficial''' Octave app available for Android in the Google Play store.  Please see [[Octave for Android]] for further  information.

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.

* https://www.octave.org/download.html

For a list of build dependencies, refer to  [[Building]].

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 known to work as well).  If you face any difficulties that you think are bugs, please report them to the [http://bugs.octave.org bug tracker], or ask for help on the [https://lists.gnu.org/mailman/listinfo/help-octave help@octave.org mailing list].

Each new Octave release introduces many new features.  A complete list of user visible changes can be seen by running <code>news</code> at the Octave prompt.

* '''What's new in the next version of Octave?'''

** See the [https://hg.savannah.gnu.org/hgweb/octave/file/tip/NEWS NEWS file] on the development branch.

* '''What was new in Octave Version X.Y.Z?'''

==How do I install or load all Octave Forge packages?==

 

 

 

 

 

 

 

==How do I automatically load a package at Octave startup?==

First 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>

To execute a script from within Octave, 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 in 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 current working directory is referred to as "." in the output of {{manual|path}}.

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 add the script's location to the current path, you can use the {{manual|run}} function instead:

<syntaxhighlight lang="octave">

run ("Script Name With Spaces.m")

run ("/opt/local/foo.m")

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:

==How do I close a figure?==  

You can control the number of displayed decimals using the {{manual|format}} command:

<syntaxhighlight lang="octave">

pi = 3.14159265358979

pi = 3.1416

==How do I call an Octave function from C++?==

Please read the manual https://www.gnu.org/software/octave/doc/interpreter/Calling-Octave-Functions-from-Oct_002dFiles.html.

One can use the function {{manual|exist}} to tell if a regular file, say <code>foo.txt</code> exist in Octave's load path, or the current directory:

 

>> exist ("foo.txt", "file")  # 2, if file exists, 0 otherwise

figure (1, "visible", "off");

plot (sin (1:100));

print -deps "/tmp/sin.eps"

</syntaxhighlight>

One can set that behavior as default:

set (0, "defaultfigurevisible", "off");

==How do I increase Octave's precision?==

Octave's default numerical type is [https://en.wikipedia.org/wiki/IEEE_754 IEEE 754] binary64, a.k.a. "double" or "hardware floats".  This type has a precision of 53 bits or about 16 decimal digits. It is supported by each modern computer hardware, so it is really '''fast'''.  This type is assumed throughout for Octave's calculations.  If more precision was required, one can obtain a "few bits more" by using integer types, e.g. {{manual|uint64}}, but in general one cannot expect more precision from any '''fast''' numerical software.  Just to visualize "how big" those numerical limits are, consider the following table:

|+ Limits of some of Octave's data types obtained by {{manual|intmax}} and {{manual|flintmax}}.

| style="text-align: right;" | <code>18,446,744,073,709,551,615</code>

| style="text-align: right;" | <code>16,777,216</code>

When working with other types than "double" in Octave, one has to make sure, that the first operand is converted to the desired type:

<syntaxhighlight lang="Octave">

>> uint64 (2^53 + 1)

</syntaxhighlight>

Notice the difference, in the first line the addition within the brackets is performed using double precision, therefore the result gets "truncated" to the maximum possible value without a warning. The third line uses throughout uint64 precision.

Consider carefully if your problem really needs more precision.  Often if you're running out of precision the problem lies fundamentally in your methods being [https://en.wikipedia.org/wiki/Numerical_stability numerically unstable], thus more precision will not help you here.

If you absolutely must have more precision, you're at present better off using a [https://en.wikipedia.org/wiki/Computer_algebra_system CAS] instead of Octave. However, CAS or symbolic computations must be implemented '''in software''' which makes it much slower than hardware floats. An example of such a CAS is [http://www.sagemath.org/ Sage] or have a look at Octave's [[Symbolic package]].

You can't. Matlab P-files (files with a <code>.p</code> file extension), also known as P-code, are [https://en.wikipedia.org/wiki/Obfuscation_%28software%29 obfuscated] files that cannot be run outside of Matlab itself. The original source Matlab m-files that were used to generate these P-files should be used in Octave instead.

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 <code>A \ x</code> will be interpreted.  Sections [http://www.octave.org/doc/interpreter/Techniques-Used-for-Linear-Algebra.html Techniques Used for Linear Algebra] and [http://www.octave.org/doc/interpreter/Sparse-Linear-Algebra.html Linear Algebra on Sparse Matrices] from the manual describe this procedure.

You are probably looking for the function {{manual|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 the first line of the help text (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 matrix:

   >> lookfor correlation

   corr                Compute matrix of correlation coefficients.

   corrcoef            Compute a matrix of correlation coefficients.

   spearman            Compute Spearman's rank correlation coefficient RHO.

Also, 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 <code>corr</code> at the octave prompt followed by pressing the {{key press|Tab}}-Key twice would suggest the following:

   >> corr

   corr     corrcoef

:''See [[Differences between Octave and Matlab]]''.

= Development =

== When will feature X be released or implemented? ==

When it's ready, sooner [https://www.octave.org/get-involved.html if you help].  You can [https://savannah.gnu.org/patch/?group=octave send us patches] if you can implement feature X yourself.  If you can't, some [https://www.octave.org/commercial-support.html developers may be convinced to work on your specific problem for some money].

:''See [[Developer FAQ]]''.

[[Category:FAQ]]