GNU Octave

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GNU Octave
GNU Octave
Developer:	John W. Eaton
Initial release:	1988
Stable release	Template:LSR
Preview release	Template:LPR
Platform:	Cross-platform
Available in:	?
Genre:	Scientific computing
License:	GNU General Public License
Website:	[[Website::http://www.gnu.org/software/octave/]]

Octave is a free computer program for performing numerical computations which is mostly compatible with MATLAB. It is part of the GNU Project.

[edit] 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.

It should be noted that the name has nothing to do with musical octaves. Octave is named after a former professor of the principal author, who was known for his ability to perform quick back-of-an-envelope calculations. ^[1]

[edit] Technical details

• Octave is written in C++ using STL libraries.
• Octave uses an interpreter to execute the Octave language.
• Octave is extensible using dynamically loadable modules.
• Octave interpreter works in tandem with gnuplot and Grace software to create plots, graphs, and charts, and to save or print them.

[edit] 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 constructs, and can be extended to support UNIX system calls and functions. However, it does not support passing arguments by reference.

Octave programs consist of a list of function calls or a script. The language is matrix-based and provides various functions for matrix operations. It is not object-oriented, but it does support various data structures.

Its syntax is very similar to MATLAB, and carefully programming a script will allow it to run on both Octave and MATLAB.

Because Octave is made available under the GNU General Public License; it may be freely copied and used. The program runs under most Unix and Unix-like operating systems, as well as Microsoft Windows.

[edit] 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. 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
x.a = 1
octave:3> x.b
x.b =

  1  2
  3  4

octave:4> x.c
x.c = string

Short-circuit boolean operators

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 `|'.

Increment and decrement operators

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

Unwind-protect

Octave supports a limited form of exception handling modeled after the unwind-protect form of Lisp. The general form of an unwind_protect block looks like this:

unwind_protect
  body
unwind_protect_cleanup
  cleanup
end_unwind_protect

Variable-length 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});
  endif
endfunction

Variable-length 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);
  endfor
endfunction

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([9000,1]):

#include <octave/oct.h>
  ...
  ColumnVector NumRands(2);
  NumRands(0) = 9000;
  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());

[edit] MATLAB compatibility

Octave has been built with MATLAB compatibility in mind. It therefore 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.

[edit] See also

• List of numerical analysis software
• Comparison of numerical analysis software

[edit] External links

Wikibooks has a book on the topic of

Octave Programming Tutorial

• Octave.org Home Page

[edit] Documentation

• Online documentation
• Octave wiki (click twice—page redirects cause some browsers to time out)
• Octave FAQ Wiki with new plotting commands
• Mailing List Archives on Nabble - Search all Octave mailing lists.
• Mailing List Archives on Gmane - Search all Octave mailing lists.

[edit] Graphical User Interfaces

• QtOctave Graphical User Interface - Matlab counterpart. Under heavy Development.
• Octave Workshop: an Octave IDE - Development stopped in 2006
• kOctave: Graphical User Interface - for the KDE Desktop (base for Octave Workshop) Development stopped in 2003

[edit] Web Interfaces

• Web Interface to Octave - Computing using GNU Octave in webbrowser
• Online access to Octave - Allows you to perform simple Octave calculation online.

[edit] Add-ons

• Octave-forge community development page - Toolboxes for various problems from independent developers.
• OctPlot - High quality 2D graphics.
• Octave graphics add-on - 3D visualization system for Octave.
• Octaviz - 3D visualization system for Octave.
• MPI Toolbox for Octave (MPITB) - Parallel Computing for Octave using MPI.

[edit] References

1. ↑ Eaton, John. About Octave. Retrieved on 2008-10-14.

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