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Hi everyone,</div>
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I am currently preprocessing my MEG data (removing artifacts). The strange thing is that when looking for jump artifacts I don't find any, but when looking for muscle artifacts I do find jump artifacts. See the code below. Here you can find 5 trials of my data,
where in the second trial there is a jump artifact (according to muscle artifact detection): <a href="http://dropcanvas.com/yp0d0" target="_blank" style="color: rgb(17, 85, 204);">http://dropcanvas.com/yp0d0</a></div>
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<div>------------------------------<wbr>------------------------------<wbr>------------------</div>
<div><i>load('data_short')</i></div>
<div><i>%% detect jump artifacts </i></div>
<div><i>cfg = [];</i></div>
<div><i> </i></div>
<div><i>% channel selection, cutoff and padding</i></div>
<div><i>cfg.artfctdef.zvalue.channel = 'MEG';</i></div>
<div><i>cfg.artfctdef.zvalue.cutoff = 20; % artifact threshold</i></div>
<div><i>cfg.artfctdef.zvalue.<wbr>trlpadding = 0; </i></div>
<div><i>cfg.artfctdef.zvalue.<wbr>artpadding = 0;</i></div>
<div><i>cfg.artfctdef.zvalue.<wbr>fltpadding = 0;</i></div>
<div><i> </i></div>
<div><i>% algorithmic parameters</i></div>
<div><i>cfg.artfctdef.zvalue.<wbr>cumulative = 'yes';</i></div>
<div><i>cfg.artfctdef.zvalue.<wbr>medianfilter = 'yes';</i></div>
<div><i>cfg.artfctdef.zvalue.<wbr>medianfiltord = 9;</i></div>
<div><i>cfg.artfctdef.zvalue.absdiff = 'yes';</i></div>
<div><i> </i></div>
<div><i>% make the process interactive</i></div>
<div><i>cfg.artfctdef.zvalue.<wbr>interactive = 'yes';</i></div>
<div><i> </i></div>
<div><i>[~, artifact_jump] = ft_artifact_zvalue_old(cfg, data_short);</i></div>
<div><i><br>
</i></div>
<div><i><br>
</i></div>
<div><i>%% Detect muscle artifacts</i></div>
<div><i>cfg = [];</i></div>
<div><i><br>
</i></div>
<div><i>% channel selection, cutoff and padding</i></div>
<div><i>cfg.artfctdef.zvalue.channel = 'MEG';</i></div>
<div><i>cfg.artfctdef.zvalue.cutoff = 4; % artifact threshold</i></div>
<div><i>cfg.artfctdef.zvalue.<wbr>trlpadding = 0; % pad at both sides of trial till it is ... seconds.</i></div>
<div><i>cfg.artfctdef.zvalue.<wbr>fltpadding = 0;</i></div>
<div><i>cfg.artfctdef.zvalue.<wbr>artpadding = 0.2; % take 0.2s padding of an artifact (of the part that is above threshold)</i></div>
<div><i><br>
</i></div>
<div><i>% algorithmic parameters</i></div>
<div><i>cfg.artfctdef.zvalue.bpfilter = 'yes';</i></div>
<div><i>cfg.artfctdef.zvalue.bpfreq = [110 140];</i></div>
<div><i>cfg.artfctdef.zvalue.bpfiltord = 9;</i></div>
<div><i>cfg.artfctdef.zvalue.<wbr>bpfilttype = 'but';</i></div>
<div><i>cfg.artfctdef.zvalue.hilbert = 'yes';</i></div>
<div><i>cfg.artfctdef.zvalue.boxcar = 0.2;</i></div>
<div><i><br>
</i></div>
<div><i>% make the process interactive</i></div>
<div><i>cfg.artfctdef.zvalue.<wbr>interactive = 'yes';</i></div>
<div><i><br>
</i></div>
<div><i>[~, artifact_muscle] = ft_artifact_zvalue_old(cfg, data_short);</i></div>
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------------------------------<wbr>------------------------------<wbr>---------------------------</div>
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Another thing is that when I only look for jump artifacts in the channel from where I know a jump is present, it actually is detected (try specifying <i>cfg.artfctdef.<wbr>zvalue.channel = 'MLF32';)</i></div>
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<i><br>
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I am using matlab2013a on the mentat cluster and I use the latest version of FieldTrip. Any help on detecting these jump artifacts is greatly appreciated.</div>
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<div style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: 12.8000001907349px; background-color: rgb(255, 255, 255);">
Best,</div>
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Mats van Es</div>
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