Saving preprocessed data in a raw MEG format

[Jed Meltzer]

Dear Geoff,

I haven't tried to do exactly what you're describing, but I have worked a lot
with CTF data and can share some thoughts on how I would go about it if I wanted
to try it.  The .ds data format is quite complex, but there is one thing that
works to your favor.  The .ds is a directory, not a single file, and the raw
data is one particular file that consists pretty much entirely of numbers (the
one called .meg4)  There are other files that contain the header information
necessary to know how to break up those raw numbers into channels, trials, etc.
 So one promising avenue would be to entirely copy the whole directory, but try
to modify the raw data while leaving everything else the same.  So if your
preprocessing is things that leave the trial structure exactly the same (e.g.
filtering, 3-rd order gradient balancing, even ICA component subtraction), then
you could just overwrite the values in the raw data and keep all the old
remaining files to have a valid and accurate .ds dataset.  I would try doing
this with a very simple operation on the data at first, such as multiplying it
by 2.
On the other hand, if your preprocessing includes rejecting trials, truncating
them, etc., then you would have a lot more to worry about.

Please post to the list again and let us know if you find a way to do it!
-Jed Meltzer
meltzerj AT nidcd.nih.gov




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Subject: FIELDTRIP Digest - 8 Jul 2010 to 13 Jul 2010 (#2010-128)

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FIELDTRIP Digest - 8 Jul 2010 to 13 Jul 2010 (#2010-128)
Table of contents:
	* Call for Papers - special issue - Academic Software Applications for
Electromagnetic Brain Mapping Using MEG and EEG

	* time-frequency analysis base line correction
	* Saving preprocessed data in a raw MEG format (3)
	* clarification (2)
	* cohrefchannel
	* Aligning head across runs
	1. Call for Papers - special issue - Academic Software Applications for
Electromagnetic Brain Mapping Using MEG and EEG
	* Call for Papers - special issue - Academic Software Applications for
Electromagnetic Brain Mapping Using MEG and EEG (07/13)
From: Robert Oostenveld <r.oostenveld at FCDONDERS.RU.NL>
	2. time-frequency analysis base line correction
	* time-frequency analysis base line correction (07/13)
From: Odelia Goldberg <odidodi at HOTMAIL.COM>
	3. Saving preprocessed data in a raw MEG format
	* Saving preprocessed data in a raw MEG format (07/13)
From: Geoff Brookshire <Geoff.Brookshire at MPI.NL>
	* Re: Saving preprocessed data in a raw MEG format (07/13)
From: "a.stolk at fcdonders.ru.nl" <a.stolk at FCDONDERS.RU.NL>
	* Re: Saving preprocessed data in a raw MEG format (07/13)
From: Laurence Hunt <lhunt at FMRIB.OX.AC.UK>
	4. clarification
	* clarification (07/13)
From: Odelia Goldberg <odidodi at HOTMAIL.COM>
	* Re: clarification (07/13)
From: "a.stolk at fcdonders.ru.nl" <a.stolk at FCDONDERS.RU.NL>
	5. cohrefchannel
	* Re: cohrefchannel (07/13)
From: Marco Rotonda <marco.rotonda at GMAIL.COM>
	6. Aligning head across runs
	* Aligning head across runs (07/13)
From: Maximilien Chaumon <maximilien.chaumon at GMAIL.COM>

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