[FieldTrip] Sign flip in lcmv spatial filter with different versions of MATLAB

[Bushra Riaz Syeda]

Hello,

Just to update, I have checked more subjects and I found that the sign flip is in a lot of subjects ( but my labels were only affected in 3 subjects).
Wouldnt this make results unreliable? as reproducibility of results is affected.

Kind regards
Bushra Riaz



________________________________
From: fieldtrip <fieldtrip-bounces at science.ru.nl> on behalf of Bushra Riaz Syeda via fieldtrip <fieldtrip at science.ru.nl>
Sent: 01 September 2021 13:25
To: FieldTrip discussion list <fieldtrip at science.ru.nl>
Cc: Bushra Riaz Syeda <bushra.riaz at gu.se>
Subject: [FieldTrip] Sign flip in lcmv spatial filter with different versions of MATLAB


Hello,



I am having a strange error. I calculated lcmv beamformer for my  Neuromag dataset couple of years ago. I ran some beamformer based analysis and now I thought I will redo some part of the analysis.

I noticed during the rerun of my scripts that the spatial filter calculated for 3 subjects ( out of 20) has a sign flip for 3-5 % of the vertices. After investigating for a week, I found that I get sign flip for these vertices when I run the same script with MATLAB 2013b and MATLAB 2017a ( fieldtrip version was same for both runs).



I have attached the figure for one of the vertex of spatial filter with both MATLAB versions.



Now my question is, as this sign flip is affecting my further analysis, I would like to know , how to figure out which one is correct and if anyone has any idea where the error could be coming from.

Thank you

Any help would be highly appreciated.



Kind regards

Bushra Riaz

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