[FieldTrip] Partial artifact rejection

Ingrid Nieuwenhuis inieuwenhuis at berkeley.edu
Wed Dec 5 19:08:52 CET 2012

Hi Patrick,

What you can do is use partial artifact rejection by calling 
ft_rejectarttifact with  cfg.artfctdef.reject = 'partial'. Then 
subsequently loop over the trials you get, and identify the ones (by 
looking at data.time{iTr}) that do not start at the time your trials 
normally start (this means it's a trial after an artifact). Finally, 
exclude those by using ft_redefinetrials.

For instance, if your trials start with t=0, then after 
ft_rejectartifact you can do something like:
ind_keep = zeros(length(data.trial),1); %allocate
for iTrl = 1:length(data.trial)
   if data.trial{iTrl}(1) ~= 0
     %this means it's a trial occurring AFTER an artifact
     ind_keep(iTrl) = false;
    %this means it's a trial occurring BEFORE an artifact
     ind_keep(iTrl) = true;

%only keep the trials before the artifact:
cfg = [];
cfg.trials = find(ind_keep);
data = ft_redefinetrial(cfg, data);

Hope this helps,

On 12/5/2012 5:57 AM, Jung, Patrick wrote:
> Dear all,
> in the reference documentation it says "In case of partial artifact 
> rejection, a minimum length of the
> resulting sub-trials can be specified."
> I'd like to reject the trial segment from the beginning of the 
> artifact onwards to keep only the data before the artifact occurred.
> But I don't want to append subtrials.
> How can I do that in fieldtrip?
> Many thanks for your help!
> Best,
> Patrick
> _______________________________________________
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> fieldtrip at donders.ru.nl
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Ingrid Nieuwenhuis PhD
Postdoctoral Fellow
Sleep and Neuroimaging Laboratory
Department of Psychology
University of California, Berkeley
California 94720-1650
Tolman Hall, room 5305

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