This section lists situations/commands where Octave behavessignificantly different from Matlab and where this is relevant forthe learning and teaching of Matlab at the School of EngineeringSciences.
Students are invited to report incompatibility issues not listed here(by email to fangohr@soton.ac.uk).
Short details of BioSig for Octave and Matlab: BioSig is an open source software library for biomedical signal processing, featuring for example the analysis of biosignals such as the electroencephalogram (EEG), electrocorticogram (ECoG), electrocardiogram (ECG), electrooculogram (EOG), electromyogram (EMG), respiration, and so on. X-Poly for Mac OS v.1.0 A software synthesizer plugin for Logic, Garage Band and Cubase employing a unique form of subtractive synthesis. The concept of the X-Poly is based around two oscillators, each containing four special sub-oscillators spaced one octave apart. The latest released version of Octave is always available from. Please download from, which will redirect automatically to a nearby mirror site.
4.1 General observations
4.1.1 Windows
I have done a few tests (creation of vectors, plotting of x andagainst y-vector, check that ode45 command exists) with version3.0 on MS Windows, and Octave seems to behave exactly like Matlab(although the ouput displayed on screen sometimes has a slightly differentformat).
Hints:
- to close a figure window, just press q (when the focus is on this window)
4.1.2 Mac OS X
The version I have tried on a Mac OS X system (although having thesame version number 3.0.0) did by default not have the octave packageodepkg installed and did therefore not know about the ode45command (but has alternative commands such as lsode that we can useinstead). All octave packages can be downloaded fromhttp://octave.sourceforge.net/packages.html and installed with pkginstall FILENAME (see octave web pages for further instructions).
4.1.3 Linux/Unix
There is of course octave for Linux (originally, Octave was developed onUnix/Linux and only later ported to Windows and Mac OS X).
Free Octave Download For Windows
4.2 ODE45 - function handle
The ode45 function in Matlab can be called like this:
or like this:
The first version passes the function name rhs as a string to theode45 function, the other one as a handle.
Octave only supports the second option, so in Octave the correspondingcommand has to read:
4.3 ODE45 - default accuracy
Matlab's default settings for allowed absolute and relative errortolerances (and related to that step size in the integration) differfrom Octave's. Octave has a larger step size. To reduce this, one canuse the following settings
Reduce the maximum allowed step size (MaxStep), and the initial step size:
(It seems that the MaxStep does not apply to the very first step-- that's why we need to set both.)
Then pass this options object vopt to the ode45 command like this:
Or reduce the absolute and/or relative tolerances to enforce smaller integration steps:
All parameters can be combined, for example:
[Tested with octave GNU Octave, version 3.0.3 on Mac OS X]
4.4 Editing m-files
A student reports that on Mac OS X, they cannot type edit myfile.mto open an editor to edit the file. The edit command (in Matlab) willstart an editor instructing it to load the file myfile.m if itexists, or creating an empty file and loading it into the editor ifthe file does not yet exist. The default editor is part of the MATLABGraphical User Interface.
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As there is no such GUI for Octave, the edit command in Octave (on anyoperating system) is likely to try to invoke the default editor thathas been defined. On Unix (this includes Linux and Mac OS X), it iscommon to set an environment variable with nameEDITOR to contain the name of the desired editor.
If you find that the edit myfile.m command does not worksatisfactorily, the simplest work around is not to use it. Instead youcan open the m-file directly in some text editor of your choice. Youneed to make sure you save the file myfile.m, before you execute the file byeither typing myfile at the Octave prompt, or calling myfile()if myfile.m contains a function.
You need to make sure the octave program is in the same workingdirectory as the file. You can use the commands pwd (Print WorkingDirectory) in octave to display the current directory and cd toChange Directory:
Any plain text editorwill do. On all platforms Emacs is available (although it might needsome getting used to): We recommend XEmacs for Windows, Emacs orXEmacs for Linux and Aquamacs for Mac OS X. All of these support syntaxhighlighting for matlab files (and also for LaTeX files).
Another often used cross-platform editor is VIM.
You can also use Textedit on Mac OS X (which is very basic but comeswith Mac OS X preinstalled), edit on Windows (which is even morebasic) or any other source code text editor (see list of these onWikipedia entry for Source code editor).
4.5 Further resources
Octave Gui Mac
See also FAQ on Matlab compatibility at http://wiki.octave.org/FAQ#Differences_between_Octave_and_Matlab
Octave Software
Another often used cross-platform editor is VIM.
You can also use Textedit on Mac OS X (which is very basic but comeswith Mac OS X preinstalled), edit on Windows (which is even morebasic) or any other source code text editor (see list of these onWikipedia entry for Source code editor).
4.5 Further resources
Octave Gui Mac
See also FAQ on Matlab compatibility at http://wiki.octave.org/FAQ#Differences_between_Octave_and_Matlab
Octave Software
Octave software, free download For Mac Os
and this Wiki entry http://en.wikibooks.org/wiki/MATLAB_Programming/Differences_between_Octave_and_MATLAB
