GNU Octave

What is GNU Octave?

GNU Octave is a powerful and high-level scientific programming language primarily used for numerical computations. It has the capability to solve both linear and non-linear problems. Also, it can easily perform other numerical experiments. In addition, it has advanced graphics capabilities for data visualization and manipulation. Octave is primarily used by its command line interface. You can also use this to write non-interactive programs. The Octave language is much more likely to be Matlab, which is why most programs are easily portable.

It is a structured programming language that is similar to C language. It supports several functions of the C standard library and a limited number of Unix system calls and functions. Octave is written in C++ using the standard C++ library. It uses an interpreter to run the Octave scripting language. It does not support passing arguments by reference. Octave programs include a list of function calls. It provides several functions for matrix operations, and the syntax is matrix-based. Octave easily supports various data structures and allows object-oriented programming. The Octave program runs on Microsoft Windows, Unix and Unix-like operating systems, including Linux, Android, macOS and iOS.

Octave can be extended with the help of dynamically loadable modules. The octave interpreter includes an OpenGL-based graphics engine that is used to create plots, graphs and charts, as well as prints and saves. You can also use gnuplot to do the same. Octave has a Graphical User Interface (GUI) in addition to the traditional command-line interface (CLI).

Features Furnishes by GNU Octave

GNU Octave has a bundle of features, which are described below.

Compatibility with the Syntax:

Octave's syntax is largely compatible with MATLAB, making it easy to transition from one to the other.

You can comment on a line using the # character as well as the % character.
There are a number of C-based operators (++, --, +=, *=, /=) that are supported.
In Octave, elements can be referenced without creating a new variable with the help of cascaded indexing.
You can define the string using the double-quote (") sign as well as the single-quote (').
When the type of the variable is single, Octave calculates the "mean" in the single domain, which is faster but does not give accurate results.
You can terminate Blocks with more specific keywords, such as endif, endfor, endwhile, etc.
You can define the functions within scripts and at the Octave prompt.
A do-until loop is present here, which is similar to do-while in C language.

The syntax is Mathematics-Oriented:

It provides a convenient command-line interface for solving linear and nonlinear problems numerically.

Preinstalled Plotting and Visualization Tools:

Octave includes high-level commands for creating 2D and 3D plots.

Cross-Platform:

It runs on various platforms, including GNU/Linux, macOS, BSD, and Microsoft Windows.

Free & Open Source:

Octave is free software licensed under the GNU General Public License (GPL).

Language and Syntax:

Octave's syntax is very similar to MATLAB, making it easy for users familiar with MATLAB to transition to Octave. It supports matrix operations, data manipulation, and a wide range of mathematical functions.

Uses:

Octave is widely used in academia and industry for numerical analysis, algorithm development, and data visualization. It's also popular for teaching and research purposes.

Plotting and Visualization:

Octave includes a powerful graphics system for creating plots, graphs, and visualizations. It supports both 2D and 3D plotting.

Extensibility:

Users can extend Octave's functionality using packages and user-defined functions. It has a vast repository of community-contributed packages available through the Octave Forge.

Interoperability:

Octave can call functions written in C++, C, Fortran, or other languages, and it can be integrated with other software tools and libraries.

Command Line and GUI:

Octave can be used both via a command-line interface and a graphical user interface (GUI), providing flexibility based on user preference.

Compatibility with MATLAB

Octave has been created with MATLAB compatibility, which provides a lot of features and functionalities.

It comes up with Matrices as fundamental data types.
Octave easily supports complex numbers.
It has several math functions and expanded function libraries.
It provides more extensibility in the form of user-defined functions.

In Octave, MATLAB is treated as a bug that's why it can be supposed as a software clone.

Compatible with Function

In GNU Octave, almost all the functions are present. Some of them are accessible through Octave Forge packages. The functions are available as part of either Forge packages or core Octave. There are also a number of unimplemented functions included in the Octave function _unimplemented.m_. There are listed unimplemented functions under several Octave forge packages in the Octave wiki.

When you call an unimplemented function, it will show the error message:

octave:1> foo

warning: the 'foo' function is not implemented in Octave

Please check <http://www.octave.org/missing.html> to learn how you can contribute to missing functionality in Octave.

error: 'foo' undefined near line 1 column 1

User Interfaces (UI)

Octave includes a graphical user interface along with an integrated development environment (IDE) which is based on Qt. It was included in the Octave 3.8 version and has been the default interface since the release of the Octave 4.0 version. There are also a number of third-party graphical front-ends, such as ToolBox, for the purpose of coding education.

GUI Applications

The user can easily create GUI applications with the help of Octave code. For example, button, edit control, checkbox:

Example

# creating a figure and panel
f = figure;

# creating a button
b1 = uicontrol(f, "style", "pushbutton", "string", "Click Me", "position", [10 20 120 30]);

# To create a text box
t1 = uicontrol(f, "style", "text", "string", "This is a label", "position", [30 60 200 30]);

# To create a radio button
r1 = uicontrol(f, "style", "radiobutton", "string", "Option 1", "position", [10 100 100 30]);

# To create a list box
l1 = uicontrol(f, "style", "listbox", "string", {"Item 1", "Item 2", "Item 3"}, "position", [30 150 120 60]);

For Textbox

% prompts for the dialog box
prompts = {"Name", "Age", "Favorite Language"};

% Defining default values
defaults = {"Anton", "25", "Black"};

% Defining initial positions and sizes
rowscols = [2, 10; 4, 6; 2, 12];

% Input dialog with the prompts, title and initial positions
user_inputs = inputdlg(prompts, "Enter Personal Information", rowscols, defaults);

Listbox and Message Box

% Options to display in the list dialog
options = {"Option 1", "Option 2", "Option 3", "Option 4"};

% A list dialog to permit user to select multiple items at once
[selected_indices, confirmed] = listdlg("ListString", options, "SelectionMode", "Multiple");

% Check if the user confirmed their selection
if (confirmed == 1)
  % If a user confirms the selection, display the selected options
  msgbox("You selected:");
  for i = 1:numel(selected_indices)
    msgbox(sprintf("\t%s", options{selected_indices(i)}));
  endfor
else
  % If a user canceled the selection
  msgbox("You canceled the selection.");
endif

RadioButtons

# To create a figure
f = figure;

# To create a button group
gp = uibuttongroup(f, "Position", [0 0.5 1 0.5]);

# To create radio buttons in the button group
b1 = uicontrol(gp, "style", "radiobutton", "string", "Option A", "Position", [20 120 120 60]);
b2 = uicontrol(gp, "style", "radiobutton", "string", "Option B", "Position", [20 70 120 60]);
b3 = uicontrol(gp, "style", "radiobutton", "string", "Option C", "Position", [20 40 120 60]);

# Create a radio button outside of the button group
b4 = uicontrol(f, "style", "radiobutton", "string", "Outside Group", "Position", [20 10 120 60]);

Command History:

Octave saves the commands so that they can be recalled and edited later if needed.

Data Structures:

Octave supports a limited amount of organizing data in structures. For this, let's take an example where we will see a structure x with elements a, b, and c (where a is an integer, b is an array, and c is a string):

Example

octave:1> x.a = 4; x.b = [5, 6; 7, 8]; x.c = "new_string";
octave:2> x.a
ans =  4

octave:3> x.b
ans =

   5   6
   7   8

octave:4> x.c

ans = new_string

octave:5> x
x =

  scalar structure containing the fields:

    a = 4
    b = 5   6
        7   8

    c = new_string

Short-circuit Boolean Operators:

Octave's && and || logical operators are evaluated in a short-circuit fashion. It is similar to the corresponding operators in the C language.

Let's take an example to understand this. You can solve systems of equations using linear algebra operations on vectors and matrices. Here is an example:

Example

x = 4;
y = 0;

% Short-circuit AND
if (x > 0) && (y > 0)
    disp('Both a and b are positive.');
else
    disp('At least one of x or y is not positive.');
end

% Short-circuit OR
if (x > 0) || (y > 0)
    disp('At least one of x or y is positive.');
else
    disp('Neither x nor y is positive.');
end

Increment & Decrement Operators:

Octave has C-like increment and decrement operators ++ and -- in both prefix and postfix forms. Octave also supports the augmented assignment operator x + = 6

Unwind-protect:

Octave includes a certain form of exception handling modeled after the unwind_protectof Lisp. An example of unwanted_protect is given below:

In Octave, 'unwind_protect' is used to ensure that certain cleanup code is always executed. It will also be executed even after occurring an error in the protected code block. This construct is similar to the 'try...catch...finally'. This pattern is found in various other programming languages.

Here's an example given on the uses of 'unwind_protect' use:

Example

unwind_protect
  % Code that can cause to produce an error
  disp('Protected code block');

  error('An error arises!');
unwind_protect_cleanup

  % This is cleanup code that should always run
  disp('Cleanup code block');
end_unwind_protect

Explanation

In the above code block of 'unwind_protect', the code is executed first. If an error arises in the protected block of code, the execution jumps to the 'unwind_protect_cleanup' block. The 'unwind_protect_cleanup' block code will always be executed anyway. Finally, the 'end_unwind_protect' shows that this is the ending of the construct.

Output:

Protected code block
Cleanup code block
An error arises!

Octave also supports try-and-catch constructs to handle exceptions and errors in the code. It allows you to catch errors and empowers you to take action without affecting your program. See the below program to get an understanding of try and catch method.

Example

try
  % Code that might cause an error
  disp('try block');

  error('An error arised!');

catch
  % Code to handle the error
  disp('catch block');

  disp(lasterr());
end

Variable Length Argument List

Octave supports handling functions that accept an unspecified number of arguments. To specify a list of zero or more arguments. Make use of varargin as the last argument in the list. Varargin is defined as a cell array that contains all the input arguments.

Example

function v = myFunction (varargin)
 
% Input arguments
  num_args = nargin;
  fprintf('Number of input arguments: %d\n', num_args);

  for k = 1:num_args
    fprintf('Argument %d: %s\n', k, num2str(varargin{k}));
  end

  % Returning the number of arguments as output
  v{1} = num_args;
end

Variable Length Return List

The varargout keyword enables you to manage Variable-length return lists. It allows a function to return a varying number of output arguments.

Example

function varargout = variableReturnExample(n)
  % outputs example
  output1 = n;
  output2 = n^2;
  output3 = n^3;
 
  % Assigning outputs to varargout
  if nargout >= 1
    varargout{1} = output1;
  end
  if nargout >= 2
    varargout{2} = output2;
  end
  if nargout >= 3
    varargout{3} = output3;
  end
end

Explanation

The 'variableReturnExample' function in the above code returns a simple number of variables based on the caller's request using the 'varargout' keyword. It accepts one input argument, 'n' and computes three possible outputs: 'out1', 'out2' and 'out3'. The program then assigns this value to 'varargout' based on the number of outputs expected by the caller. If at least one output is required, assign 'out1' to 'varraout{1}'; if two, it also returns 'out2' for 'varargout{2}'; If it is triple, it returns 'out3' to 'varargout{3}'.

Integration with C++

It is also possible to execute Octave code directly in a C++ program. For example, here is a code snippet for calling.

Example

#include <octave/oct.h>

ColumnVector NumRands(3);
NumRands(0) = 10;
NumRands(1) = 4;
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());

Explanation

The code snippet above uses the Octave C++ API to invoke the 'rand' function. Next, a ColumnVector named NumRands with 2 elements is created, starting with the values 10 and 1. An octave_value_list f_arg is created, which has NumRands as its first argument and then calls the feval function to perform the Octave rand function with F_arg and expects the product. The result stored in f_ret is converted to a Matrix called unis. This enables a 10x1 matrix of random numbers using the Octave rand function in a C++ program.

How do I install GNU Octave on Linux?

To install GNU Octave on Linux, you can go with the following methods:

Install GNU Octave Using Package Manager

Open the terminal by using the shortcut keys Ctrl + Alt + T./
Update the package list using the given command for Debian-based Linux distros:

Command

Update the package list for CentOS/RHEL-based Linux distros:

Command

Install Octave in Debian-based Linux distros:

Command

Install Octave for CentOS/RHEL-based Linux distributions:

Command

Manual Method:

Visit the official GNU Octave website and download the source tarball.
After downloading the tarball, extract it using the given command:

Command

In the above command, replace x.y.z with the actual Octave version of GNU.

Now, navigate to the extracted directory:

Command

After that, Configure, compile, and install by going with the given command:

Command

./configure
make
sudo make install

Install GNU Octave Using Flatpak Method:

First, install Flatpak by running the given command if it has not already been installed (for Debian-based distros):

Command

Install GNU for CentOS/RHEL-based Linux-based OS:

Command

Now, add the Flathub repository:

Command

flatpak remote-add --if-not-exists flathub
https://flathub.org/repo/flathub.flatpakrepo

Install Octave:

Command

How do I install GNU Octave on Windows?

To install GNU Octave on Windows, follow these steps:

Go to the GNU Octave website and navigate to the download section.
From there, download the GNU Octave.
In the next window, click on MS Windows.
Then, click on the Octave 6.4.0 installer.exe button to download the .exe file.

GNU Octave includes several useful packages that enhance its functionality. Here are those packages:

The Image Package consists of several functions which are used for image processing.
The Control Package It provides tools for computer-aided control system design (CACSD) based on the SLICOT Library.
The Dataframe Package is almost similar to the data.frame of the R programming language. It is a must useful package for data manipulation.
The Econometrics Package includes maximum likelihood estimation (MLE) and generalized method of moments (GMM) techniques.
The VLFeat Package implements popular computer vision algorithms like HOG, SIFT, k-means, etc..
LIBSVM and LIBLINEAR package libraries are used to support vector machines and machine learning techniques.
GeoPDEs Package is used for isogeometric analysis in partial differential equations which is related to mathematics.
Instrument-Control Package provides low-level I/O functions for a number of interfaces, such as serial, i2c, and much more.

History of GNU Octave

The idea for GNU Octave was given by James B. Rawlings and John G. Ekerdt in 1998 while preparing for a chemical reactor design course. They needed a software tool to accompany their course and found existing solutions not sufficient. In 1992, John W. Eaton, a former student of Rawlings, started working on the project as part of his Ph.D. thesis. The initial development was funded by the Department of Energy and the National Science Foundation.

The first alpha version of GNU Octave was released in 1994. The software was intended to be a free alternative to MATLAB, which was widely used but proprietary. In 1996, GNU Octave 1.0 was officially released. This version provided basic functionalities and established Octave as a valuable tool for numerical computations. In the early 2000s, Octave continued to develop and added more functions. Improved performance and increased compatibility with MATLAB. The user community grew, contributing to the development and support of the software.

In 2007, GNU Octave adopted the GNU General Public License (GPL) version 3. This ensured that Octave remained free and open-source. In 2010, Octave released some significant improvements in graphics and user interface. The development of the GUI started. It makes Octave more accessible to new users. In 2015, Octave 4.0 was released. This version includes a graphical user interface (GUI) for the first time. This was an important change that made Octave more user-friendly.

In 2017, Octave 4.2 included a major overview of the plotting system, which made it more efficient and compatible with MATLAB's plotting functions. In 2018, Octave 5.0 was released, introducing several new features and performance improvements. Octave continues to evolve with frequent updates and improvements. The focus has been on enhancing performance, improving compatibility with MATLAB, and expanding the functionality of the software.

Conclusion

GNU Octave is a robust and open-source technique to MATLAB. This programming language is excel in numerical computations and data visualization as well as. With its MATLAB syntax, substantial functionality, and strong community assist, it provides both educational and business services. The versatility and simplicity of Octave make it unique for the analysis of numerical and the development of algorithms.

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