Importing 4-D datasets

Nathan Weisz weisz at LYON.INSERM.FR
Fri Jan 11 14:28:40 CET 2008

hi gopa,

> between EEG and MEG as the EEG electrodes were not digitized. So it is
> exported as one large 171 channel file.


and then:
you shoud see which sensors / electrodes correspond to which row in  
your data matrix.

> Would you happen to know how many files pdf2set will export and with
> what extensions? I have ascii files of the data sets, I saw an .xyz
> file (cartesian coordinates) and an elp file (electrode position)  
> file.

next to the data and the xyz you should have the header-file (m4d). if  
you want to do dipole fits you also need the headshape file (hs_file;  
read it via read_bti_hs).
[just a side note: if it's a simple dipole fit you want then the 4d  
software should be good enough, so why go through the pain of  
exporting and importing data]

> Can I use the last two files in conjunction with the standard 10-20
> electrode system position to read in the EEG data?

I am not quite sure if i understand you correctly. but many fieldtrip  
functions (e.g. definetrial, timelockanalysis, freqanalysis) allow you  
to specifiy the channels you want, e.g.:{'MEG'};

you may try:{'EEG'};
and see if it only applies the relevant functions to the EEG channels  
(i haven't done this myself). if not you can specify all labels by  
hand or add something to the channelselction.m function that suits  
your needs.

regarding electrode positions on the fieldtrip-FTP (standard_BEM)  
there are standard 10-20 and 10-05 elc files. you can read those files  
using read_fcdc_elec.

hope this helps,

Dr. Nathan Weisz

INSERM - Unité 821
Dynamique cérébrale et cognition
Centre Hospitalier Le Vinatier, Bâtiment 452
95 Boulevard Pinel
69500 Bron, France

Tel: ++33 - (0)4 - 7213 8915
Email: weisz at
Chat-AV: nathanweisz at

Please avoid sending me Word or PowerPoint attachments.

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 and
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