eeglab2fieldtrip

[Robert Oostenveld]

Hi Valesca

On 13 Jul 2007, at 11:02, Valesca Kooijman wrote:
> In connection with your previous advice concerning the
> eeglab2fieldtrip script, we came accross the following problem and
> solution (see script below):
> ...
>
> I do still get the following warning after running the above script:
>
> Warning: writing segmented data as if it were continuous
> In fieldtrip-20070710\private\write_brainvision_eeg at 38
> In fieldtrip-20070710\private\write_data at 63
> In write_fcdc_data at 48
> In ConversionEEGDATA at 13
>
> Is this problematic or is this a standard warning following
> conversion to Vision Analyzer?

The warning relates to the problem that you indicated in your email
further down (i.e. the data being assumed to be ntrials X nchans X
nsamples). I.e. if your data is indeed ntrials X nchans X nsamples,
then you don't have to worry. In your case, you should worry (see
below).

> In addition, I was wondering where my trial onset markers are
> written to? Write_fcdc_data only generates a .eeg and a .hdr file,
> and not a .vmrk file.

They are not writen. You could manually write a vmrk file (they are
ascii files). The format is like the snippet below

Brain Vision Data Exchange Marker File, Version 1.0
[Common Infos]
DataFile=pp01_pilot_load0_3s.seg
[Marker Infos]
; Each entry: Mk<Marker number>=<Type>,<Description>,<Position in
data points>,
; <Size in data points>, <Channel number (0 = marker is related to
all channels)>,
; <Date (YYYYMMDDhhmmssuuuuuu)>
; Fields are delimited by commas, some fields might be omited (empty).
; Commas in type or description text are coded as "\1".
Mk1=New Segment,,1,1,0,20050315114252667836
...

> From your earlier emails I understood that the datamatrix should be
> converted to ntrials X nchans X nsamples before running
> write_fcdc_data.  Currently my datamatrix consists of nchans X
> nsamples X ntrials.  Would you mind letting me know how I can
> convert my datamatrix? Thanks a lot.

I just made a change to write_brainvision_eeg, please update to the
latest FT release. In that function it still expects the data to be
ntrials X nchans X nsamples, i.e.
    ntrl  = size(dat,1);
    nchan = size(dat,2);
    nsmp  = size(dat,3);
You can use the matlab function permute (see "help permute") to swap
the dimensions in EEG.data by permute(EEG.data, [3 1 2]).

Robert

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