question on data formats

[Robert Oostenveld]

Hi Silvia,

I am doing a CC of this mail to the discussion list, since other
people may be interested in it as well. Please continue through the
maliing list.

On 7 Sep 2006, at 10:53, Silvia Gennari wrote:
> Thanks very much for your prompt response. I will write to the list
> as you suggest. I just wanted to ask you one more thing so I
> understand what is involved.
>
> It seems from what you are saying that if I get the MEG data, the
> triggers, and coil positions into some text format, then it would
> be OK.  I can  see in the raw files (in text viewers) the kind of
> information we have.

I forgot to mention that you also need the coil orientations. But
yes, that information would be sufficient, and it does not matter
whether that information comes from binary or from text files.

Besides this information, it would be convenient to have additional
information, like the position of the coils used for head
localization (I am not sure how that is done for BTi, but I presume
in a similar fashion as CTF). And it is convenient to read the
auxiliary files that are generated with the BTi software, e.g. the
MRI file and the head model file. But the data represented in those
files can all be generated and managed inside FT.

> Also, I do open the data in Matlab, and I have some functions that
> are trying to do some basic kind of analysis.  So the problem is
> not reading the data into MAtlab but the kind of assumptions that
> Fieldtrip makes regarding the layout of the information.

Fieldtrip works with data structured in particular ways. The most
basic data structure from where most analysis start is that of raw
data, which is the output of PREPROCESSING. Have a look at http://
www2.ru.nl/fcdonders/fieldtrip/doku.php?
id=fieldtrip:documentation:dataformats, which I just updated.
Furthermore, have a look at http://www2.ru.nl/fcdonders/fieldtrip/
doku.php?id=fieldtrip:documentation:tutorial:introduction and
especially figure 3 to see how the functions interact and how the
data flows.

Other fieldtrip functions, such as TIMELOCKANALYSIS, FREQANALYSIS and
SOURCEANALYSIS also have relatively fixed output structure. As long
as you use data structures that are fieldtrip-like, you can use
fieldtrip functions on them.

best,
Robert