[FieldTrip] Jump artifacts not detected

Schoffelen, J.M. (Jan Mathijs) jan.schoffelen at donders.ru.nl
Fri Jul 10 18:27:29 CEST 2015

Hi Mats,
It all pertains, as I implied earlier, to what the data looks like after the application of the specific algorithmic parameters (and the Z-scoring). I think the discussion would benefit if you show us some screenshots with the ‘interactive’ figure that illustrates your problem. Note that you pasted code in an earlier e-mail that used ft_artifact_zvalue_old. In my comment with respect to a newer version of the code, I meant the use of the suffix ‘old’.


On Jul 10, 2015, at 2:19 PM, Es, M.W.J. van (Mats) <M.vanEs at donders.ru.nl<mailto:M.vanEs at donders.ru.nl>> wrote:

Hi Jan Matthijs,

I do not think that the problem lies in the size of the jump: when I artificially create a very large jump in my data the jump is also not detected, see code.

data_short.trial{1}(132,1:700)=0; %channel 132 is MRC11
data_short.trial{1}(132,701:1441)=1; %data 'jumps' up to 1 and stays there (massively bigger jump than actual squid jump).
You are right that if the 'muscle' algorithm picks up the jump, there is no problem. However, I don't know if this algorithm picks up the jumps consistently. (I did find 10 jumps in one dataset and zero in another, which I know is plausible but still).

About my code: could you refer me to the newer version of the code? The code I use was on the fieldtrip tutorial (http://www.fieldtriptoolbox.org/tutorial/automatic_artifact_rejection).

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Jan-Mathijs Schoffelen, MD PhD, Senior researcher

Max Planck Institute for Psycholinguistics
Donders Centre for Cognitive Neuroimaging

E-mail: j.schoffelen at donders.ru.nl<mailto:j.schoffelen at donders.ru.nl>
Telephone: +31-24-3614793


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