 GNU Octave

GNU Octave
GNU Octave screenshotDeveloper(s) John W. Eaton Initial release 1988 Stable release 3.4.3 (October 10, 2011 ) _{[+/−]} Preview release 3.3.54 (November 19, 2010 )^{[1]} _{[+/−]} Written in C, C++ Platform Crossplatform Available in 19 languages Type Scientific computing License GNU General Public License Website gnu.org/software/octave/ GNU Octave is a highlevel language, primarily intended for numerical computations. It provides a convenient commandline interface (CLI) for solving linear and nonlinear problems numerically, and for performing other numerical experiments using a language that is mostly compatible with MATLAB. It may also be used as a batchoriented language. As part of the GNU Project, it is free software under the terms of the GNU General Public License (GPL).
Contents
History
The project was conceived around 1988. At first it was intended to be a companion to a chemical reactor design course. Real development was started by John W. Eaton in 1992. The first alpha release dates back to January 4, 1993 and on February 17, 1994 version 1.0 was released. Version 3.0 was released on December 21, 2007.
The program is named after Octave Levenspiel, a former professor of the principal author who was known for his ability to perform quick backoftheenvelope calculations.^{[2]}
Deployments
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 vulnerability related to guessing social security numbers.^{[3]}
Technical details
 Octave is written in C++ using the Standard Template Library (STL).
 Octave uses an interpreter to execute the Octave scripting language.
 Octave is extensible using dynamically loadable modules.
 Octave interpreter works with gnuplot and Grace software to create plots, graphs, and charts, and to save or print them.
Octave, the language
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.^{[4]} However, it does not support passing arguments by reference.^{[5]}
Octave programs consist of a list of function calls or a script. The syntax is matrixbased and provides various functions for matrix operations. It is not objectoriented, but it does support various data structures.
Its syntax is very similar to MATLAB, and careful programming of a script will allow it to run on both Octave and MATLAB.^{[6]}
Because Octave is made available under the GNU General Public License, it may be freely changed, copied and used.^{[2]} The program runs under most Unix and Unixlike operating systems, as well as Mac OS X and Microsoft Windows.^{[7]}
Notable features
Command and variable name completion
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.
Command history
When running interactively, Octave saves the commands typed in an internal buffer so that they can be recalled and edited.
Data structures
Octave includes a limited amount of support for organizing data in structures. For instance:
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 = { a = 1 b = 1 2 3 4 c = string }
Shortcircuit boolean operators
Octave's '
&&
' and '
' logical operators are evaluated in a shortcircuit fashion (like the corresponding operators in the C language), in contrast to the elementbyelement operators '&
' and '
'.Increment and decrement operators
Main article: Increment and decrement operatorsOctave includes the Clike increment and decrement operators '
++
' and '
' in both their prefix and postfix forms. Also augmented assignment.Unwindprotect
Octave supports a limited form of exception handling modelled after the '
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 '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 purposely inserted within the exception_handling code).Variablelength argument lists
Octave has a real 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.function s = plus (varargin) if (nargin==0) s = 0; else s = varargin{1} + plus (varargin{2:nargin}); end end
Variablelength return lists
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
C++ integration
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])
:#include <octave/oct.h> ... 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());
MATLAB compatibility
Octave has been built with MATLAB compatibility in mind, and shares many features with MATLAB:
 Matrices as fundamental data type.
 Builtin support for complex numbers.
 Powerful builtin math functions and extensive function libraries.
 Extensibility in the form of userdefined functions.
There are a few purposeful, albeit minor, differences:
 Comment lines can be prefixed with the # character as well as the % character
 Various Cbased operators ++, , +=, *=, /= are supported
 Elements can be referenced without creating a new variable, e.g. [1:10](3)
 Strings can be defined with the " character as well as the ' character
See also
 List of numerical analysis software
 Comparison of numerical analysis software
 List of statistical packages
 List of numerical libraries
Further reading
 Hansen, Jesper (June 2011). GNU Octave Beginner's Guide. Packt Publishing.
External links
 Octave.org Home Page
Documentation
 Online documentation.
 Octave wiki (Click twice – page redirects cause some browsers to time out).
 Reviewed entry in the Free Software Directory.
 GNU Octave FAQ Wiki with new plotting commands^{[dead link]}
 Mailing List Archives on Nabble – Search all Octave mailing lists.
 Mailing List Archives on Gmane – Search all Octave mailing lists.
 Italian Octave Community.
Numerical packages and libraries interfacing with GNU Octave
GNU Octave is also powered by thirdparty tools and libraries, mostly providing general or domainspecific abstractions for scientific computing. Those tools may be categorized according whether their contributions are more oriented toward computational modelling or toward enhancing visual analysis.
Numerical tools
 Octaveforge community development page – Free software toolboxes for various problems from independent developers. A Windows installer for both GNU Octave and the toolboxes is also available.
 Mastrave project – Crosslanguage library (GNU GPLv3+ covered) compatible with GNU Octave and Matlab, to ease environmental modelling with general purpose semantic array programming utilities.
 Neuroimaging Analysis Kit – Library (MIT License covered) to process neuroimaging data within GNU Octave or Matlab, particularly functional magnetic resonance images. It also offers a Pipeline system to handle multistage processing.
 Parallel Matlab Toolbox – Matlab language data structures and functions which implement distributed Matlab arrays. It is released under MIT license.
 MPI Toolbox for Octave (MPITB) – Parallel Computing for Octave using MPI.
Plotting tools
 PLPlot – A replacement of the traditional gnuplot in GNU Octave, licensed under the GNU LGPL.
 OctPlot – High quality 2D graphics (postscript and screen graphics). Released under GNU GPL.
 Octave graphics addon – 3D visualization system for Octave.
 Octaviz – 3D visualization system for GNU Octave (wrapper that makes VTK classes accessible from within GNU Octave). It also provides highlevel functions for 2D visualization. (Note: Their site says, "Unfortunately, Octaviz is no longer in development. The latest release (0.4.7) was quite usable and stable when built against vtk5.0.")
User interfaces
Octave does not come with a graphical user interface (GUI)/integrated development environment (IDE) by default. Instead, an additional graphical frontend must be installed.
Graphical user interfaces (GUI)
 An official graphical interface based on Qt has now been migrated to the main source repository and will likely be released with Octave 4.0.^{[citation needed]}
 GUIOctave (Windows) — GUIOctave provides a convenient Graphical User Interface to simplify the use of GNU Octave for user who don't like the original command line based version of GNU Octave, but still want to use the GNU Octave potential.
 Kalculus (Linux) — Matlab like UI for GNU Octave and Yacas written in Qt4 with Ruby bindings
 Xoctave (Windows, Linux) — Xoctave encapsulates GNU Octave using pipes and provides extra tools to make using it easier. Its UI is very similar to that of Matlab.
 OctaveNB — NetBeans IDE integration for GNU Octave (since 2009)  features SVN, local history, diff, multi language projects from the NetBeans IDE for your Octave development
 QtOctave Graphical User Interface (Windows, Linux) — A GUI with Matlab style.
 Cantor is a free software mathematics application for scientific statistics and analysis with builtin support for Octave. It is a part of the KDE project.
Web user interfaces (WUI)
 Online LaTeX and Octave Editor  Online Octave/Matlab editor with plotting and storage capabilities.
 Online access to Octave – Allows you to perform simple Octave calculations online.
 MathCloud – Share Matlab/Octave scripts and data and do your computations in the cloud.
References
 ^ "Octave News Archive". http://www.gnu.org/software/octave/news.html.
 ^ ^{a} ^{b} Eaton, John W. "About Octave". http://www.gnu.org/software/octave/about.html. Retrieved 20090628.
 ^ HPC, July 8, 2009.
 ^ "GNU Octave  Controlling subprocesses". November 14, 2008. http://www.networktheory.co.uk/docs/octave3/octave_269.html. Retrieved Jan 28, 2009.
 ^ "GNU Octave". http://www.delorie.com/gnu/docs/octave/octave_105.html. Retrieved Jan 28, 2009.
 ^ "FAQ: MATLAB compatibility". http://www.gnu.org/software/octave/FAQ.html#MATLABcompatibility. Retrieved July 4, 2009.
 ^ "FAQ: Getting Octave". http://www.gnu.org/software/octave/FAQ.html#GettingOctave. Retrieved July 4, 2009.
GNU Project History Licenses Software Public speakers Other topics Numerical software Free Software Proprietary List of numerical analysis software · Comparison of numerical analysis software Categories: Data analysis software
 GNU Project software
 Numerical programming languages
 Free mathematics software
 Free software programmed in C++
 Linux numerical analysis software
 Array programming languages
 Free crossplatform software
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