GNU Octave

The project was conceived around 1988.{{cite web|title=About GNU Octave|url=https://www.gnu.org/software/octave/about.html|website=www.gnu.org|publisher=GNU|access-date=1 May 2018}} At first it was intended to be a companion to a chemical reactor design course. Full development was started by John W. Eaton in 1992. The first alpha release dates back to 4 January 1993 and on 17 February 1994 version 1.0 was released. Version 9.2.0 was released on 7 June 2024.{{Cite web |date=2024-06-07 |title=Octave 9.2.0 Released |url=https://octave.org/news/release/2024/06/07/octave-9.2.0-released.html |access-date=2024-11-05 |website=octave.org |language=en}}

The program is named after Octave Levenspiel, a former professor of the principal author. Levenspiel was known for his ability to perform quick back-of-the-envelope calculations.{{cite web

| last = Eaton

| first = John W

| title = About Octave

| url = https://www.gnu.org/software/octave/about.html

| access-date = 2009-06-28 }}

In addition to use on desktops for personal scientific computing, Octave is used in academia and industry. For example, Octave was used on a massive parallel computer at Pittsburgh Supercomputing Center to find vulnerabilities related to guessing social security numbers.{{cite web

|url=http://www.hpcwire.com/industry/government/Social-Security-Number-Vulnerability-Findings-Relied-on-Supercomputing-50292227.html

|title=Social Security Number Vulnerability Findings Relied on Supercomputing

|date=8 July 2009

|archive-url=https://web.archive.org/web/20120229220547/http://www.hpcwire.com/hpcwire/2009-07-08/social_security_number_vulnerability_findings_relied_on_supercomputing.html

|archive-date=29 February 2012

}}

Acceleration with OpenCL or CUDA is also possible with use of GPUs.{{Cite web|url=https://developer.nvidia.com/blog/drop-in-acceleration-gnu-octave/|title=Drop-in Acceleration of GNU Octave|date=June 5, 2014|website=NVIDIA Developer Blog}}

• Octave is written in C++ using the C++ standard library.
• Octave uses an interpreter to execute the Octave scripting language.
• Octave is extensible using dynamically loadable modules.
• Octave interpreter has an OpenGL-based graphics engine to create plots, graphs and charts and to save or print them. Alternatively, gnuplot can be used for the same purpose.
• Octave includes a graphical user interface (GUI) in addition to the traditional command-line interface (CLI); see #User interfaces for details.

The Octave language is an interpreted programming language. It is a structured programming language (similar to C) and supports many common C standard library functions, and also certain UNIX system calls and functions.{{cite web

| url = http://www.network-theory.co.uk/docs/octave3/octave_269.html

| title = GNU Octave - Controlling subprocesses

| access-date = 2009-01-28

| date = 14 November 2008

| archive-url = https://web.archive.org/web/20090107005339/http://www.network-theory.co.uk/docs/octave3/octave_269.html

| archive-date = 7 January 2009

| url-status = dead

}} However, it does not support passing arguments by reference{{cite web

| url = http://www.delorie.com/gnu/docs/octave/octave_105.html

| title = GNU Octave

| access-date = 2009-01-28

}} although function arguments are copy-on-write to avoid unnecessary duplication.

Octave programs consist of a list of function calls or a script. The syntax is matrix-based and provides various functions for matrix operations. It supports various data structures and allows object-oriented programming.{{cite web

| url = https://www.gnu.org/software/octave/NEWS-3.2.html

| title = Summary of important user-visible changes for version 3.2

| access-date = 2012-01-05

}}

Its syntax is very similar to MATLAB, and careful programming of a script will allow it to run on both Octave and MATLAB.{{cite web

| url = http://www.octave.org/wiki/index.php?title=FAQ#Porting_programs_from_Matlab_to_Octave

| title = FAQ: MATLAB compatibility

| access-date = 2009-04-04

| archive-date = 2011-11-21

| archive-url = https://web.archive.org/web/20111121043348/http://octave.org/wiki/index.php?title=FAQ#Porting_programs_from_Matlab_to_Octave

| url-status = dead

}}

Because Octave is made available under the GNU General Public License, it may be freely changed, copied and used. The program runs on Microsoft Windows and most Unix and Unix-like operating systems, including Linux, Android, and macOS.{{cite web

| url = http://www.octave.org/wiki/index.php?title=FAQ#On_what_platforms_does_Octave_run.3F

| title = FAQ: Getting Octave

| access-date = 2009-04-04

| archive-date = 2011-11-21

| archive-url = https://web.archive.org/web/20111121043348/http://octave.org/wiki/index.php?title=FAQ#On_what_platforms_does_Octave_run.3F

| url-status = dead

}}{{Cite web|url=https://octave.org/doc/v6.3.0/|title=Top (GNU Octave (version 6.3.0))|website=octave.org}}{{Cite web|title=Octave for Android - Octave|url=https://wiki.octave.org/Octave_for_Android|access-date=2021-08-23|website=wiki.octave.org}}

Typing a TAB character on the command line causes Octave to attempt to complete variable, function, and file names (similar to Bash's tab completion). Octave uses the text before the cursor as the initial portion of the name to complete.{{cite web|url=https://www.gnu.org/software/octave/doc/interpreter/Commands-For-Completion.html#Commands-For-Completion|title=Letting Readline Type For You|work=GNU Octave Reference Manual|last=Eaton|first=John W.|access-date=2016-07-29|archive-date=2018-02-12|archive-url=https://web.archive.org/web/20180212145842/http://www.gnu.org/software/octave/doc/interpreter/Commands-for-Completion.html#Commands-For-Completion|url-status=dead}}

When running interactively, Octave saves the commands typed in an internal buffer so that they can be recalled and edited.

Octave includes a limited amount of support for organizing data in structures. In this example, we see a structure {{mono|x}} with elements {{mono|a}}, {{mono|b}}, and {{mono|c}}, (an integer, an array, and a string, respectively):

octave:1> x.a = 1; x.b = [1, 2; 3, 4]; x.c = "string";

octave:2> x.a

ans = 1

octave:3> x.b

ans =

1 2

3 4

octave:4> x.c

ans = string

octave:5> x

x =

scalar structure containing the fields:

a = 1

b =

1 2

3 4

c = string

Octave's && and || logical operators are evaluated in a short-circuit fashion (like the corresponding operators in the C language), in contrast to the element-by-element operators & and |.

{{Main|Increment and decrement operators}}

Octave includes the C-like increment and decrement operators ++ and -- in both their prefix and postfix forms.

Octave also does augmented assignment, e.g. x += 5.

Octave supports a limited form of exception handling modelled after the [http://www.lispworks.com/documentation/HyperSpec/Body/s_unwind.htm unwind_protect] of Lisp. The general form of an unwind_protect block looks like this:

unwind_protect

body

unwind_protect_cleanup

cleanup

end_unwind_protect

As a general rule, GNU Octave recognizes as termination of a given block either the keyword end (which is compatible with the MATLAB language) or a more specific keyword endblock or, in some cases, end_block. As a consequence, an unwind_protect block can be terminated either with the keyword end_unwind_protect as in the example, or with the more portable keyword end.

The cleanup part of the block is always executed. In case an exception is raised by the body part, cleanup is executed immediately before propagating the exception outside the block unwind_protect.

GNU Octave also supports another form of exception handling (compatible with the MATLAB language):

try

body

catch

exception_handling

end

This latter form differs from an unwind_protect block in two ways. First, exception_handling is only executed when an exception is raised by body. Second, after the execution of exception_handling the exception is not propagated outside the block (unless a rethrow( lasterror ) statement is explicitly inserted within the exception_handling code).

Octave has a mechanism for handling functions that take an unspecified number of arguments without explicit upper limit. To specify a list of zero or more arguments, use the special argument varargin as the last (or only) argument in the list. varargin is a cell array containing all the input arguments.

function s = plus (varargin)

if (nargin==0)

s = 0;

else

s = varargin{1} + plus (varargin{2:nargin});

end

end

A function can be set up to return any number of values by using the special return value varargout. For example:

function varargout = multiassign (data)

for k=1:nargout

varargout{k} = data(:,k);

end

end

It is also possible to execute Octave code directly in a C++ program. For example, here is a code snippet for calling rand([10,1]):

1. include

...

ColumnVector NumRands(2);

NumRands(0) = 10;

NumRands(1) = 1;

octave_value_list f_arg, f_ret;

f_arg(0) = octave_value(NumRands);

f_ret = feval("rand", f_arg, 1);

Matrix unis(f_ret(0).matrix_value());

C and C++ code can be integrated into GNU Octave by creating oct files, or using the MATLAB compatible MEX files.

Octave has been built with MATLAB compatibility in mind, and shares many features with MATLAB:

1. Matrices as fundamental data type.
2. Built-in support for complex numbers.
3. Powerful built-in math functions and extensive function libraries.
4. Extensibility in the form of user-defined functions.

Octave treats incompatibility with MATLAB as a bug; therefore, it could be considered a software clone, which does not infringe software copyright as per Lotus v. Borland court case.

MATLAB scripts from the MathWorks' FileExchange repository in principle are compatible with Octave. However, while they are often provided and uploaded by users under an Octave compatible and proper open source BSD license, the FileExchange Terms of use prohibit any usage beside MathWorks' proprietary MATLAB.{{Cite web |title=FAQ - Octave |url=https://wiki.octave.org/FAQ |access-date=2022-12-05 |website=wiki.octave.org}}{{Cite web |title=MATLAB Central Terms of Use |url=https://www.mathworks.com/matlabcentral/content/terms-of-use.html |access-date=2022-12-05 |website=www.mathworks.com |language=en}}{{Cite web |title=File Exchange Licensing FAQ |url=https://www.mathworks.com/matlabcentral/content/fx/fx-transition-faq.html |access-date=2022-12-05 |website=www.mathworks.com |language=en}}

There are a few purposeful, albeit minor, [http://octave.org/wiki/index.php?title=FAQ#Porting_programs_from_Matlab_to_Octave syntax additions] {{Webarchive|url=https://web.archive.org/web/20120426060857/http://octave.org/wiki/index.php?title=FAQ#Porting_programs_from_Matlab_to_Octave |date=2012-04-26 }}:

1. Comment lines can be prefixed with the # character as well as the % character;
2. Various C-based operators ++, --, +=, *=, /= are supported;
3. Elements can be referenced without creating a new variable by cascaded indexing, e.g. [1:10](3);
4. Strings can be defined with the double-quote " character as well as the single-quote ' character;
5. When the variable type is single (a single-precision floating-point number), Octave calculates the "mean" in the single-domain (MATLAB in double-domain) which is faster but gives less accurate results;
6. Blocks can also be terminated with more specific Control structure keywords, i.e., endif, endfor, endwhile, etc.;
7. Functions can be defined within scripts and at the Octave prompt;
8. Presence of a do-until loop (similar to do-while in C).

Many, but not all, of the numerous MATLAB functions are available in GNU Octave, some of them accessible through packages in [https://octave.sourceforge.io Octave Forge]. The functions available as part of either core Octave or Forge packages are listed [https://octave.sourceforge.io/list_functions.php?q=&sort=alphabetic online] {{Webarchive|url=https://web.archive.org/web/20240314051049/https://octave.sourceforge.io/list_functions.php?q=&sort=alphabetic |date=2024-03-14 }}.

A list of unavailable functions is included in the Octave function [http://hg.savannah.gnu.org/hgweb/octave/file/tip/scripts/help/__unimplemented__.m __unimplemented.m__]. Unimplemented functions are also listed under many Octave Forge packages in the [https://wiki.octave.org/Category:Octave_Forge Octave Wiki].

When an unimplemented function is called the following error message is shown:

octave:1> guide

warning: the 'guide' function is not yet implemented in Octave

Please read to learn how you can contribute missing functionality.

error: 'guide' undefined near line 1 column 1

Octave comes with an official graphical user interface (GUI) and an integrated development environment (IDE) based on Qt. It has been available since Octave 3.8,{{Cite web|url=https://www.gnu.org/software/octave/NEWS-3.8.html|title=GNU Octave Version 3.8|website=www.gnu.org}} and has become the default interface (over the command-line interface) with the release of Octave 4.0.

It was well-received by an EDN contributor, who wrote "[Octave] now has a very workable GUI" in reviewing the then-new GUI in 2014.{{cite web |last=Hageman |first=Steve |date=7 February 2014 |title=GNU Octave hits a high note |url=http://www.edn.com/electronics-blogs/the-practicing-instrumentation-engineer/4428091/GNU-Octave-hits-a-high-note |website=EDN}}

Several 3rd-party graphical front-ends have also been developed, like ToolboX for coding education.

With Octave code, the user can create GUI applications. See [https://octave.org/doc/v7.1.0/GUI-Development.html GUI Development (GNU Octave (version 7.1.0))]. Below are some examples:

Button, edit control, checkbox

1. create figure and panel on it

f = figure;

1. create a button (default style)

b1 = uicontrol (f, "string", "A Button", "position",[10 10 150 40]);

1. create an edit control

e1 = uicontrol (f, "style", "edit", "string", "editable text", "position",[10 60 300 40]);

1. create a checkbox

c1 = uicontrol (f, "style", "checkbox", "string", "a checkbox", "position",[10 120 150 40]);

Textbox

prompt = {"Width", "Height", "Depth"};

defaults = {"1.10", "2.20", "3.30"};

rowscols = [1,10; 2,20; 3,30];

dims = inputdlg (prompt, "Enter Box Dimensions", rowscols, defaults);

Listbox with message boxes.

my_options = {"An item", "another", "yet another"};

[sel, ok] = listdlg ("ListString", my_options, "SelectionMode", "Multiple");

if (ok == 1)

msgbox ("You selected:");

for i = 1:numel (sel)

msgbox (sprintf ("\t%s", my_options{sel(i)}));

endfor

else

msgbox ("You cancelled.");

endif

Radiobuttons

1. create figure and panel on it

f = figure;

1. create a button group

gp = uibuttongroup (f, "Position", [ 0 0.5 1 1])

1. create a buttons in the group

b1 = uicontrol (gp, "style", "radiobutton", "string", "Choice 1", "Position", [ 10 150 100 50 ]);

b2 = uicontrol (gp, "style", "radiobutton", "string", "Choice 2", "Position", [ 10 50 100 30 ]);

1. create a button not in the group

b3 = uicontrol (f, "style", "radiobutton","string", "Not in the group","Position", [ 10 50 100 50 ]);

Octave also has many packages available. Those packages are located at Octave-Forge [https://octave.sourceforge.io/packages.php Octave Forge - Packages], or [https://gnu-octave.github.io/packages/symbolic GitHub Octave Packages]. It is also possible for anyone to create and maintain packages.

Alternatives to GNU Octave under an open source license, other than the aforementioned MATLAB, include Scilab and FreeMat.{{cite book|last=Trappenberg|first=Thomas|title=Fundamentals of Computational Neuroscience|year=2010|publisher=Oxford University Press|isbn=978-0-19-956841-3|page=361}}{{cite book|last1=Muhammad|first1=A|last2=Zalizniak|first2=V|title=Practical Scientific Computing|url=https://archive.org/details/practicalscienti00muha|url-access=limited|year=2011|publisher=Woodhead Publishing|isbn=978-0-85709-226-7|page=[https://archive.org/details/practicalscienti00muha/page/n11 3]}}{{cite book|last1=Megrey|first1=Bernard A.|last2=Moksness|first2=Erlend|title=Computers in Fisheries Research|url=https://archive.org/details/computersfisheri00megr|url-access=limited|year=2008|publisher=Springer Science & Business Media|isbn=978-1-4020-8636-6|page=[https://archive.org/details/computersfisheri00megr/page/n351 345]}}{{cite book|last=Kapuno|first=Raul Raymond|title=Programming for Chemical Engineers Using C, C++, and MATLAB|year=2008|publisher=Jones & Bartlett Publishers|isbn=978-1-934015-09-4|page=365}} Octave is more compatible with MATLAB than Scilab is,{{cite book|last=Herman|first=Russell L.|title=A Course in Mathematical Methods for Physicists|year=2013|publisher=CRC Press|isbn=978-1-4665-8467-9|page=42}}{{cite book|last1=Wouwer|first1=Alain Vande|last2=Saucez|first2=Philippe|last3=Vilas|first3=Carlos|title=Simulation of ODE/PDE Models with MATLAB, Octave and Scilab: Scientific and Engineering Applications|year=2014|publisher=Springer|isbn=978-3-319-06790-2|pages=114–115}} and FreeMat has not been updated since June 2013.{{cite web |title=FreeMat |url=http://freemat.sourceforge.net/ |website=freemat.sourceforge.net |access-date=22 February 2020}}

Also the Julia programming language and its plotting capabilities has similarities with GNU Octave.

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{{Reflist|30em}}

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