Octave

Summary
This article contains information about the installation, configuration and use of GNU Octave.
Related
Matlab
Sage-mathematics
Mathematica

From the official website:

GNU Octave is a high-level interpreted language, primarily intended for numerical computations. It provides capabilities for the numerical solution of linear and nonlinear problems, and for performing other numerical experiments. It also provides extensive graphics capabilities for data visualization and manipulation. Octave is normally used through its interactive command line interface, but it can also be used to write non-interactive programs. The Octave language is quite similar to Matlab so that most programs are easily portable.

Installation

Octave can be installed with the package octave, available in the official repositories.

Octave-Forge

Octave provides a set of packages, similar to Matlab's Toolboxes, through Octave-Forge. Some of these packages may be found in the AUR (search packages). A non-exhaustive list:

• Image — Provides functions for processing images.

http://octave.sourceforge.net/image/index.html || octave-image

• Statistics — Provides additional statistical functions.

http://octave.sourceforge.net/statistics/index.html || octave-statistics

• IO — Provides input and output in external formats such as XML, CSV or XLS.

http://octave.sourceforge.net/io/index.html || octave-io

• Signal — Provides functions for processing images

http://octave.sourceforge.net/image/index.html || octave-signal

• Multicore — Provides functions for parallel processing on multiple cores.

http://octave.sourceforge.net/multicore/index.html || octave-multicore

A complete list can be found on Octave-Forge.

Packaging

Creating an Octave-forge package for Arch is easy using the Octave-forge helper scripts for Archlinux.

Using Octave's installer

Packages can also be managed using Octave's installer. To install a package:

1. Download the .tar.gz package from Octave-Forge.
2. Install it from Octave as user by executing:

octave:1> pkg install packagename.tar.gz

Packages have dependencies which you have to install before installing your package, if you want to bypass this use:

octave:2> pkg install -no-deps packagename.tar.gz

To uninstall a package:

octave:3> pkg uninstall packagename.tar.gz

Some packages get loaded automatically by Octave, for those which do not:

octave:4> pkg load packagename

or

octave:5> pkg load all

To see which packages have been loaded use pkg list, the packages with an asterisk are the ones that are already loaded.

Plotting

Octave has two official plotting backends:

• Gnuplot — A classic Linux plotting utility.

http://www.gnuplot.info/ || gnuplot

• FLTK Backend — A new experimental OpenGL backend based on the FLTK GUI toolkit.

http://www.gnu.org/software/octave/ || octave

Note: To enable the FLTK backend, you need to install the fltk package.

GnuPlot is still the default, but it can be changed by:

octave:1> graphics_toolkit("fltk");

To make this change permanent add it to your ~/.octaverc file.

Graphical interfaces

There are very few graphical interfaces for Octave and none of them are official:

• Cantor — A graphical user interface that delegates its mathematical operations to one of several back ends (Scilab, Maxima, Octave and others).

http://edu.kde.org/cantor/ || kdeedu-cantor

• QtOctave — A Qt frontend for Octave.

https://forja.rediris.es/projects/csl-qtoctave/ || qtoctave

Reading Microsoft Excel Spreadsheets

There are several ways to read Microsoft Excel files with Octave.

Converting to an open format

The easiest way to use .xls files in Octave would be to convert them to .csv or .ods using Calc (limited to 1024 columns) from Libreoffice or Sheets(limited to 32768 columns) from the the Calligra Suite.

After the conversion is complete you can use the build-in Octave function csvread for .csv files:

octave:1> csvread('myfile.csv');

For .ods files the octave-io package is necessary which contains the odsread function:

octave:1> odsread('myfile.ods');

For .xlsx files you can use the xlsx2csv package from AUR:

 xlsx2csv -t /path/to/save/location -x /path/to/myfile.xlsx 

Reading xls files directly from Octave

If you must work with XLS files and you cannot convert them to CSV or ODS, for whatever reason, you can use the xlsread function from the octave-io package.

xlsread is Java-based and as such requires some Java libraries to enable support for XLS files.

The steps necessary to make it work are:

1. Install jdk7-openjdk, available in the official repositories.

Note: A common problem is that Octave cannot find the JDK path. To fix this execute the following commands in your shell:

$ export JAVA_HOME=/usr/lib/jvm/java-7-openjdk

You may also want to add this to your ~/.bashrc and append it to your PATH.

2. Install a Java XLS library for xlsread. There are more such libraries available, a comparison can be found at here. The recommended library is apache-poi, available in the AUR.

3. Finally, install the octave-java package from AUR.

To check if Java is working correctly in Octave, see the output of:

 octave:1> javaclasspath 
  STATIC JAVA PATH
     - empty -
  DYNAMIC JAVA PATH
     - empty -

To load the selected library in Octave, check if it is in the Java path. If not:

 octave:1> javaaddpath path/to/file.jar

In the case you chose apache-poi, the relevant JAR files can be found in /usr/share/java/apache-poi/poi-3.x.jar and /usr/share/java/apache-poi/poi-ooxml-3.x.jar.

To check if it works

 octave:1> chk_spreadsheet_support 

The output should be > 0:

                   0 No spreadsheet I/O support found
                 ---------- XLS (Excel) interfaces: ----------
                   1 = COM (ActiveX / Excel)
                   2 = POI (Java / Apache POI)
                   4 = POI+OOXML (Java / Apache POI)
                   8 = JXL (Java / JExcelAPI)
                  16 = OXS (Java / OpenXLS)
                 --- ODS (OpenOffice.org Calc) interfaces ----
                  32 = OTK (Java/ ODF Toolkit)
                  64 = JOD (Java / jOpenDocument)
                 ----------------- XLS & ODS: ----------------
                 128 = UNO (Java / UNO bridge - OpenOffice.org)

To make this permanent add the javaaddpath commands to your ~/.octaverc file.