[Eeglablist] importing huge data

[Morgan Hough]

Yuko,

If the raw data (the NetStation recording) is 1-1.5 GB then the .mat file
will be double that size and Matlab (on most systems) brings all the data
into memory and can only use 2GB.

I have had similar problems with 275 channel MEG datasets or very
long/high sampling rate EEG datasets. I would try downsampling the data in
NetStation and see if that helps. Maybe even use a smaller file
and follow the same export/import procedure. If that works then at least
you know it is an OS/Matlab issue.

I hear that Matlab 7 on Windows XP will handle 3GB with tweaking. We are
using Matlab on Tru64 (no longer supported) which can handle a lot more.
Although the G5 is a 64 bit processor and it has 4GB of RAM it can't
really use it yet (still a 32 bit OS until 10.4).

Hope that helps.

Take care,

-Morgan

On Wed, 22 Sep 2004, Yuko Yotsumoto wrote:

> Hi,
>
> We are trying to import files from our eeg experiment with 256
> channels * 500Hz * about 100 minutes. The data size is huge. The raw
> data range 1 - 1.5 GB.
>
> Net Station was used to record EEG signals, and to export files for
> further analysis with eeglab.
> We first tried to create .mat file, but the file size exceeded the
> limitations of Net Station.
>
> Then, we exported data to .RAW EGI continuous files(), and imported
> this file to eeglab.
> pop_readegi() gave the following error message.
> "Maximum variable size allowed by the program is exceeded."
>
> Looks like we do not have enough Memory. More specifically, the
> program stopped around 140th line in readegi.m, where it creates
> matrix TrialData = zeros(FrameVals,nframes); The FrameVals was about
> 270, and nframes was about 2800000. We got the same error message by
> using segmented .RAW EGI files (with smaller values for FrameVals and
> nframes).
>
> We tried these with PowerMac G4/1GB RAM, and PowerMacG5/4GB RAM, neither worked.
>
> Have anybody had the same problem? Is it possible to analyze our data
> with eeglab, or should we give up? Any alternative strategies? Our
> collaborator has BESA, and BESA can handle our data. But we are hoping
> to use eeglab for further analysis.
>
> Any suggestion will be appreciated.
> Yuko
>
> --
> -------------------------------------
> Yuko Yotsumoto     yuko at brandeis.edu
> Volen Center for Complex Systems
> Brandeis University
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