Problem with data from BESA

Robert Oostenveld r.oostenveld at FCDONDERS.RU.NL
Wed Nov 16 22:25:41 CET 2005

On 16-nov-2005, at 18:56, Michael Wibral wrote:

>  Both files also have a different order from the 10-10 layout used
> in Fieldtrip, but I guess layout files match electrodes per name,
> don't they. I will try to figure out a workaround.

Channel matching is indeed done on name and not on number/index. This
applies for the channel names in the layout file, but also for the
channel names in the electrode file. It means that the channel
ordering in either layout-file or elec-structure can be different
from the channel ordering in the data, since both the data and the
elec contain labels that can be matched when needed (e.g when
plotting or dipole fitting). The elec-structure can also contain more
or less electrode positions+labels than the EEG itself, e.g. when you
have measured bipolar ECG or EOG along (without position), or when
you have additional fiducials or electrodes in your cap that were
recorded with a polhemus but not recorded as EEG channel.

Since the sfp file is very simple and can hardly be read incorrectly,
I suspect that the error in the assignment in channel names occurs in
reading the ERP file.


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