# Running EEGLAB on Octave

As of August, 2018 EEGLAB scripts written for MATLAB can be run on the open source application Octave. Octave-compatible EEGLAB functions are available only in EEGLAB 15 - at the time of writing, the current developer version of EEGLAB - which is freely available from [github]. To run EEGLAB on Octave, one must call EEGLAB functions from the Octave command line. The EEGLAB graphic user interface (GUI) and functions that create interactive pop-up windows still do not run on Octave. However, scripts that call EEGLAB *pop_* functions should still work and plot results if their pop-up interactive window function is not engaged.

## How to install and open Octave

Download the latest version of Octave from this page. EEGLAB has been best tested using Octave 4.4, but should also run on later versions.

Then start Octave. Some Octave modules need to be installed for EEGLAB to function properly. Octave needs to be started with the option *--traditional* to ensure maximal compatibility with Matlab. From the command line, start Octave using:

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octave --traditional

This option is likely available from the Octave GUI settings (if you are using the Octave GUI). Then, you will need to install the Octave signal processing package. If the signal processing package is not installed, about 5% of EEGLAB functions will not run. On the Octave command line, type:

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pkg install -forge control pkg install -forge signal pkg load signal

Note that you need to run the last command *pkg load signal* every time you start Octave from the command line. (If you are using the Octave graphic interface there might be a way to load it automatically). You may also install the statistics toolkit although this is not critical. This toolbox is used for study statistics when present.

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pkg install -forge io pkg install -forge statistics pkg load statistics

Make sure Octave uses the “fltk” graphic toolkit. Note that this library might not be available by default and might require to recompile Octave, a process that is automatic (using on OS X *brew install octave* for example) but can last several hours.

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octave:1> graphics_toolkit ans = fltk

## Known issues with EEGLAB and Octave graphics compatibility

All EEGLAB signal processing functions will run on Octave. Although Octave is relatively compatible with Matlab for functions purely performing computations, the Octave graphic rendering engine sometimes cannot render all the subtleties of EEGLAB graphics. In particular, we have encountered the following issues:

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- EEGLAB interactive pop-up windows and the eegplot() interactive data scrolling function are not functional

- Head plots are missing a shadow property (see figure below right - facial feature shadowing is absent)
- Plug-ins need to be installed manually (downloaded as zip files and uncompressed in the EEGLAB plugins folder). Most plug-ins (including SIFT and LIMO) have not been tested on Octave and will likely not be functional. They could probably be made functional by their developers or by motivated users...
- Memory mapping functions are not functional (this is a minor limitation as this is beta functionality in EEGLAB)

As long as you are using EEGLAB command line functions, all EEGLAB plotting functions should be functional. This includes all EEGLAB scripts that run on Matlab. If you find an EEGLAB script that does not run not, please submit an EEGLAB bug report. Even some of the most complex EEGLAB plots can be rendered on Octave - for example, on the left a complex 3-D dipole plot (plotted by *dipplot*) is shown.

Octave is still actively evolving and might support a more complete graphics environment in future. Also, Matlab code can often be modified to be more Octave compatible. If you modify an interactive EEGLAB function for that purpose and want others to benefit from your changes, fork the code and create a pull request as explained on this page. This page contains other information on how to contribute to EEGLAB.

## Simple example: an EEGLAB script run in Octave

As mentioned previously, any EEGLAB Matlab script should now run under Octave.

Below is a time-frequency decomposition plotted by Octave 4.4 for the EEGLAB tutorial dataset by the EEGLAB/Matlab code below. The plot below is provided for illustrative purposes only; we had to implement some minor changes to make the EEGLAB time-frequency function *newtimef()* compatible with Octave (since the changes were also compatible with MATLAB itself, we placed them in the main repository). Other EEGLAB functions (even signal processing functions) may also still require minor changes to run under Octave.

% cd xxxxx/eeglab % move to the proper directory/folder % octave --traditional % start Octave eeglab % call EEGLAB EEG = pop_loadset('sample_data/eeglab_data_epochs_ica.set'); % load an EEGLAB dataset [ersp itc imbase time freqs] = newtimef(EEG.data(1,:,:), ... EEG.pnts, [-1000 2000], EEG.srate, [3 0.5]); % compute and plot a trial-average ERSP

For comparison, below is the graphic output of *newtimef()* run in Matlab.