[FieldTrip] fieldtrip plugin cannot find combineclusters.mexw64

Thu Mar 19 08:13:51 CET 2026

Dear Tim,

Sorry to hear about your troubles. EEGLAB gets shipped with a ‘light’ copy of FieldTrip, and the version that you reference is already almost 3 years old. I.e. it’s both a light version and it’s old. Also, given that you report troubles with so-called mex-files (on Windows) adds another dimension of complexity…

Mex-file related errors are a known pain in the head, particularly on the windows operating system. Indeed, one solution then would be to try and compile the files on your computer. The fact that you get the message that the source files cannot be found probably is the consequence of the ‘light’ version of the toolbox that is in your eeglab distro.

What I would try next, is to download a proper and up-to-date version of FieldTrip, and then do:
1) copy over the combineClusters.mexw64 to D:\eeglab2025.1.0\Fieldtrip-lite250523\private\ and run the code again. Perhaps it’s a different mex-file, and your problem goes away altogether.

otherwise

2) try to run ft_compile_mex from the downloaded fieldtrip toolbox (this requires you to start from a clean matlab path, and only add the path to fieldtrip + execute ft_defaults -> see the website for more instructions about this). The downloaded toolbox should contain all source code necessary for compilation. If your windows setup allows for mex’ification (not a guarantee though, and since I am not a windows user myself I can only be of limited help) then this might work.

Also, referring to what you called a ‘dead link’, I would reach out to the eeglab folks. If this is a known issue, you’re probably not the only one enountering it.

Good luck,
Jan-Mathijs

On 18 Mar 2026, at 20:13, Redepenning, Tim via fieldtrip <fieldtrip at science.ru.nl> wrote:

Dear list members,
Eeglab cannot find the combineclusters.mexw64 module.
Here's what I did:
In the STUDY tool of eeglab I created a study with two conditions.
I precomputed the channel measures (ITC).
For an individual channel I can use the cluster correction provided by the fieldtrip-lite plugin.
But if I average over frequency band and time to create topographies I get an error:
"EEGLAB error in function findcluster() at line 133:
Invalid MEX-file 'D:\eeglab2025.1.0\Fieldtrip-lite250523\private\combineClusters.mexw64'. The specified module could not be found." In fact, my matlab is in German, so the wording might be slightly different.
All other correction methods work.
In an earlier study this worked just fine. Since then the computer has been completely wiped and updated. Hence, Windows and some other software changes were made. The hardware has not been changed.

In the brainstorm forum (https://neuroimage.usc.edu/forums/t/invalid-mex-file/17648/2<https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fneuroimage.usc.edu%2Fforums%2Ft%2Finvalid-mex-file%2F17648%2F2&data=05%7C02%7Cfieldtrip%40science.ru.nl%7C54128acf942244fe587108de858712c3%7C084578d9400d4a5aa7c7e76ca47af400%7C1%7C0%7C639095012342425605%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=5E9E1qRcLPYlAOm0Rqv34OsirayFK6Ke0n7D697Actg%3D&reserved=0>) someone said that this issue has been fixed through the mailing list with reference to an earlier message - unfortunately, the provided link is dead.

I tried recompiling the mex-files with ft_compile_mex. Here's the output:
"Skipping up-to-date MEX file compat/matlablt2010b/@uint64/abs
Skipping up-to-date MEX file compat/matlablt2010b/@uint64/min
Skipping up-to-date MEX file compat/matlablt2010b/@uint64/max
Skipping up-to-date MEX file compat/matlablt2010b/@uint64/plus
Skipping up-to-date MEX file compat/matlablt2010b/@uint64/minus
Skipping up-to-date MEX file compat/matlablt2010b/@uint64/times
Skipping up-to-date MEX file compat/matlablt2010b/@uint64/rdivide
Error: source file for deepcopy cannot be found.
Error: source file for increment cannot be found.
Error: source file for setzero cannot be found.
Error: source file for ft_omri_smooth_volume cannot be found.
Error: source file for sap2matlab cannot be found.
Error: source file for ft_getopt cannot be found.
Error: source file for read_16bit cannot be found.
Error: source file for read_24bit cannot be found.
Error: source file for lmoutr cannot be found.
Error: source file for ltrisect cannot be found.
Error: source file for plinproj cannot be found.
Error: source file for ptriproj cannot be found.
Error: source file for routlm cannot be found.
Error: source file for solid_angle cannot be found.
Error: source file for meg_leadfield1 cannot be found.
Error: source file for splint_gh cannot be found.
Error: source file for plgndr cannot be found.
Error: source file for ft_spike_sub_crossx cannot be found.
Error: source file for rename cannot be found.
Error: source file for getpid cannot be found.
Error: source file for nanmean cannot be found.
Error: source file for nanstd cannot be found.
Error: source file for nanvar cannot be found.
Error: source file for nansum cannot be found.
Error: source file for nanstd cannot be found.
Error: source file for det2x2 cannot be found.
Error: source file for inv2x2 cannot be found.
Error: source file for mtimes2x2 cannot be found.
Error: source file for sandwich2x2 cannot be found.
Error: source file for combineClusters cannot be found.
Skipping up-to-date MEX file external/fileexchange/CalcMD5
Error: source file for mxSerialize_cpp cannot be found.
Error: source file for mxDeserialize_cpp cannot be found."

Apparently, the compiling function cannot find the module either.
Any help would be greatly appreciated.

Best wishes,
Tim Redepenning

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