GNU Octave

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GNU Octave

GNU Octave
Developed by John W. Eaton
Initial release 1988
Stable release 3.0.3  (October 10, 2008) [+/−]
Preview release 3.0.1  (April 21, 2008) [+/−]
Written in C++
Platform Cross-platform
Available in ?
Type Scientific computing
License GNU General Public License

Octave is a computer program for performing numerical computations which is mostly compatible with MATLAB. It is part of the GNU Project. It is free software under the terms of the GNU General Public License.


[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 functions, and also certain UNIX system calls and functions.[2] However, it does not support passing arguments by reference.[3]

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 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.[4]

Because Octave is made available under the GNU General Public License, it may be freely copied and used.[5] The program runs under most Unix and Unix-like operating systems, as well as Microsoft Windows.[6]

[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 (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
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.


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:

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

[edit] External links

[edit] Documentation

[edit] Graphical User Interfaces

[edit] Web Interfaces

[edit] Add-ons

[edit] References

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