Error trying to get started with get_chanlocs plugin for EEGLAB "Unrecognized function or variable 'placeFiducials'"

Hello,

I am very new to MATLAB, so apologies in advance if this is a trivial question. My university has recently acquired a Structure Sensor 3 scanner, and we would like to use the 3D models to conduct source localisation. It looks like get_chanlocs is the perfect tool to get the locations of the channels on the 3D models, but I am running into issues when trying to open the models in EEGLAB.

After importing my EEG data (.bdf file, from a Biosemi system, 64 channels), I use the "Locate electrodes in a 3D head image" option. First, I am prompted to select my 3D model, where I choose the .obj file created with the 3D scanner. Then I am asked if I want to use a template; since I do not have one yet, I select "No, I will select locations in order". At this point, MATLAB gives me this error:

Unrecognized function or variable 'placeFiducials'.

Error in get_chanlocs (line 177)

fiducials = placeFiducials(head_surface);

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I think it means there is a function (placeFiducials) that the script is trying to use, but cannot find. But I am not sure where this function should be located. Am I missing a plugin, or could this be an issue with version compatibility?

I am currently using:

- MATLAB R2025b

- EEGLAB 2025.1.0

- FieldTrip 20250106

Installed EEGLAB plugins:

- Biosig v3.8.4

- ERPLAB v12.10

- clean_rawdata v2.11

- ICLabel v1.7

- firfilt v2.8

- dipfit v5.6

- EEG-BIDS v10.3

- get_chanlocs v4

- NFT v2.2

Thanks in advance if anyone can help me with this.

Answer 1

[Anjaneyulu Bairi]

Hi,

I see that you're encountering errors related to the "placeFiducials" function. Please try the following troubleshooting steps to resolve the issue:

1) Verify the File Path:

Ensure that the placeFiducials file is included in your MATLAB path. You can check this by running:

which placeFiducials

If the output points to a MATLAB installation directory, the file is correctly added. If not, add the file to your path using:

addpath('path_to_the_file')

2) Refresh the Toolbox Cache:

Rehash the toolbox cache by running the following commands:

rehash toolboxcache
restoredefaultpath

3) Reinstall Plugins:

If the above steps don’t resolve the problem, try reinstalling the plugins you mentioned to see if that fixes the issue.

[Remi]

Hello,

Thank you very much for your reply. I apologize for the delay in mine.

The issue is that I do not have the placeFiducials file. I think it is supposed to be a function of the get_chanlocs package, but it is nowhere to be seen. That is why I suspected a version incompatibility of some kind. I have tried reinstalling everything, but that did not solve the problem.

[Walter Roberson]

(Unfortunately I am not able to locate any placeFiducials matlab source code.)