[FieldTrip] 4d data reading (248 sensor MEG system)

[jan-mathijs schoffelen]

Hi Mehmet,

It looks like you are working on a windows-machine. I have never tried  
to read in 4D-data on a windows machine, but it looks like a windows  
matlab thing.
The error message states that the second input argument to fseek (i.e.  
nbytes2-32) needs to be of class double, whereas it is represented in  
the file as e 4 byte integer.
Could you try if the following works: change the end of line 176 from  
'uint32=>double' and report back to me whether this works (just send  
it to me personally; not to the whole list)?
I will then test whether this change also works on linux/mac and will  
commit this change to the release version of FieldTrip.

I noticed in the past that indeed the 'noise-reduced' files cannot be  
directly read (mainly due to sparse documentation of the file format).  
However, fieldtrip contains a function "ft_denoise_pca", which is  
doing exactly the same as the 4D command-line programs "cfw" and "afw".

I hope this helps,

Jan-Mathijs



On Mar 10, 2011, at 7:35 PM, Mehmet-Akif Coskun wrote:

> Hi Jan,
>
>
>    Thanks for the reply. I tried reading from the raw data as  
> suggested in the link and i always getting an error like below.
>
>
> hdr=ft_read_header('E:\fieldtrip_data\c,rfhp0.1Hz')
>
>
> ?? Error using ==> fseek
> Offset must be of class double
>
>
> Error in==> fileio\private\read_4d_hdr_at_183
>          fseek(fid,nbytes2 - 32, 'cof');
>
>
> Error in ==> ft_read_header_at_246
>        orig                   = read_4d_hdr(datafile,configfile)
>
>
>
>
> the data that i try to read is raw data (unprocessed) but still i  
> can't read. Previously i was trying the data that has been processed  
> to remove environmental noise in 4d meg system sofware, and that  
> didnt work too.
>
>
> Which part i am missing?
>
>
> Thanks
> Mehmet
>
> ----- Original Message -----
> From: jan-mathijs schoffelen <jan.schoffelen at donders.ru.nl>
> Date: Thursday, March 10, 2011 2:46 am
> Subject: Re: [FieldTrip] 4d data reading (248 sensor MEG system)
> To: Email discussion list for the FieldTrip project <fieldtrip at donders.ru.nl 
> >
>
> > Hi Mehmet,
>
>
>
>
> > Please have a look at http://fieldtrip.fcdonders.nl/getting_started/bti 
> .
> >
>
> > I would not recommend the .xyz/.m4d variant, but would directly  
> read from the raw data files. Support for .xyz/.m4d files (these  
> files contain relevant header information) is implemented in  
> fieldtrip just for backward compatibility. These need to be created  
> from the raw data (using the pdf2set command (see the software  
> manual of the MEG-system for reference)), but contain only limited  
> header information (e.g. the balancing coefficients are not  
> extracted). To me this sounds like double work, because FieldTrip  
> can read the header information from the raw files directly.
> >
>
> > Good luck,
> >
>
> > Jan-Mathijs
> >
>
> >
>
> >
>
> >
>
>
> > On Mar 10, 2011, at 6:36 AM, Mehmet-Akif Coskun wrote:>
>> > Hello Dear Fieldtrip users,
>> >
>> >
>> >        I am a newbie in fieldtrip. I am having trouble reading  
>> the 4d data in fieldtrip. We are using a 248 sensor 4D MEG system.  
>> I have followed the discussion list and tried the suggestions but  
>> haven't succeeded reading the data. As far as i understand, i need  
>> some files (.xyz and .m4d) to be able to read the data but i don't  
>> also know how to obtain these files. Can anyone explain me the  
>> steps that i need to follow?
>> >
>> >
>> > Thanks in advance,
>> > Mehmet
>>
>> > _______________________________________________
>> > fieldtrip mailing list
>> > fieldtrip at donders.ru.nl
>> > http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
> >
> >
>
> Dr. J.M. (Jan-Mathijs) Schoffelen
>
> > Donders Institute for Brain, Cognition and Behaviour,
> > Centre for Cognitive Neuroimaging,
> > Radboud University Nijmegen, The Netherlands
>
> > J.Schoffelen at donders.ru.nl
>
> > Telephone: 0031-24-3614793> >
>
> > _______________________________________________
> > fieldtrip mailing list
> > fieldtrip at donders.ru.nl
> > http://mailman.science.ru.nl/mailman/listinfo/fieldtrip  
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip

Dr. J.M. (Jan-Mathijs) Schoffelen
Donders Institute for Brain, Cognition and Behaviour,
Centre for Cognitive Neuroimaging,
Radboud University Nijmegen, The Netherlands
J.Schoffelen at donders.ru.nl
Telephone: 0031-24-3614793

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