automatic EOG rejection

Ingrid Nieuwenhuis ingrid.nieuwenhuis at DONDERS.RU.NL
Fri Aug 7 15:08:06 CEST 2009


Dear Lars,

The error message means that fetch_data tries to fetch data outside of your
trials where there is no data supplied in the input data file. Fetch_data
was recently changed and now puts NaNs where there is no data. But filtering
data with NaNs is not a good idea, therefore the warning.

What happens is in artifact_eog is that the data is padded, or better said,
there is an attempt to pad the data. This is done to avoid filter artifact
at the edges, and for optimal artifact detections at/just over the border
(which can influence filtering). This padding doesn't work because in the
input data you supplied there is no extra data which can be used for
padding. Therefore the NaN's or the error that not all samples are present
in the data.

Would you can do is epoch the data into trials after artifact detection. So
first detect and reject artifacts, and then use redefinetrial (give the trl
you have now) to epoch the data.

Hope this helps,
Best Ingrid

> -----Original Message-----
> From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On
> Behalf Of Lars Meyer
> Sent: Friday, August 07, 2009 2:23 PM
> To: FIELDTRIP at NIC.SURFNET.NL
> Subject: [FIELDTRIP] automatic EOG rejection
> 
> dear all,
> 
> (newest fieldtrip, newest matlab)
> 
> trying automatic EOG artifact rejection, i get the following error:
> 
> In fetch_data at 111
> In artifact_zvalue at 213
> In artifact_eog at 179
> Warning: data contains NaNs, no filtering applied
> 
> 
> workflow was (these all worked):
> 
> - reading continous data to memory
> - merging EOG channels (from V+/V_ / H+/H_ to eogv and eogh)
> - appending EOG channels
> - re-refercing
> - filtering
> - epoching according to triggers
> 
> 
> while trying automatic rejection comes the error; visual rejection just
> works fine. in the olf fieldtrip version, the error message said "not all
> samples are present in the data". i checked the data structure; the merged
> EOG channels have been correctly appended and labelled. attached is my
> code, thanks a lot in advance!
> 
> 
> all best,
> lars
> 
> 
> Lars Meyer | MSc
> Max Planck Institute for Human Cognitive & Brain Sciences
> Department of Neuropsychology
> Stephanstra├če 1a
> 04103 Leipzig | Germany
> 
> Office | +49 (0)341 99 40 22 66
> Fax | +49 (0)341 99 40 22 60
> Mobile | +49 (0)175 113 76 65
> Home | +49 (0)341 974 26 49
> Mail | lmeyer at cbs.mpg.de
> Web | www.cbs.mpg.de/~lmeyer
> 
> ----------------------------------
> The aim of this list is to facilitate the discussion between users of the
> FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG
> and EEG analysis. See also
> http://listserv.surfnet.nl/archives/fieldtrip.html and
> http://www.ru.nl/neuroimaging/fieldtrip.

----------------------------------
The aim of this list is to facilitate the discussion between users of the FieldTrip  toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis. See also http://listserv.surfnet.nl/archives/fieldtrip.html and http://www.ru.nl/neuroimaging/fieldtrip.



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