[FieldTrip] Question about how to reduce the file size (Caspar, Emilie)

[Haiteng Jiang]

Hi  Emilie,
     You can read  each channel and then  down sample.   In the end , you
append all the channel. For more information and how to , you can refer to
the FAQ:
http://fieldtrip.fcdonders.nl/faq/how_can_i_preprocess_a_dataset_that_is_too_large_to_fit_into_memory
.

       Hope this helps,
            Haiteng

On 13 December 2014 at 12:00, <fieldtrip-request at science.ru.nl> wrote:
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>    1. Correction baseline : removing the mean value or high-pass
>       filtering ? (Kristensen Emmanuelle)
>    2. Question about how to reduce the file size (Caspar, Emilie)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 12 Dec 2014 15:49:10 +0100
> From: Kristensen Emmanuelle
>         <emmanuelle.kristensen at gipsa-lab.grenoble-inp.fr>
> To: FieldTrip discussion list <fieldtrip at science.ru.nl>
> Subject: [FieldTrip] Correction baseline : removing the mean value or
>         high-pass filtering ?
> Message-ID: <548B0066.3090309 at gipsa-lab.grenoble-inp.fr>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> Hi,
> I would need your opinion, please.
> Generally, the baseline correction means to remove a mean value from
> each epoch. I am wondering if a high pass filter, applied on the whole
> recorded signal, can perform the baseline correction.
> What do you think?
> Regards
> Emmanuelle
>
> --
> Emmanuelle KRISTENSEN
> Doctorante au Gipsa-Lab
> Equipe VIBS
>
>
>
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> Message: 2
> Date: Fri, 12 Dec 2014 22:24:17 +0000
> From: "Caspar, Emilie" <e.caspar at ucl.ac.uk>
> To: "fieldtrip at science.ru.nl" <fieldtrip at science.ru.nl>
> Subject: [FieldTrip] Question about how to reduce the file size
> Message-ID: <484FAA32-F84A-4BD2-8928-C07265183751 at live.ucl.ac.uk>
> Content-Type: text/plain; charset="us-ascii"
>
> Dear Fieltrippers,
> I did a pilot study on one participant today. Now that I'm trying to
> analyze my data, I realize that the size file is too big for my computer
> (size = 3Gb). Even after one hour, the filters (high pass + low pass) were
> not yet achieved.
>
> So I would like to see how to reduce the size of my sample BEFORE the
> filters.
>
> I know that there is "ft_resampledata", and I did it to reduce the actual
> sample rate (= 2048) to 256. However, even with this procedure my computer
> is crashing (even with 16 Go RAM). In addition, I'm not sure that I can
> resample before filtering (I read different informations).
>
> Another way I was thinking about was to pre-select electrodes that I need
> (only 6 electrodes on 64). But here I have two questions:
> - Can I pre-process only some electrodes? Does it really reduce size for
> next preprocesses?
> - Is this the correct way to ask? As it crashes, not sure it works.
>
>     cfg             = [];
>     cfg.dataset     = [ file.name];
>     cfg.channel     = 'B5', 'B6', 'B15', 'B16';
>     allData_prepross = ft_preprocessing(cfg);
>     cfg.resamplefs = 256;
>     DataSample = ft_resampledata(cfg, allData_prepross)
>
>
> I would appreciate pieces of advice!
>
> Many thanks :)
>
> Emilie
>
>
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> End of fieldtrip Digest, Vol 49, Issue 12
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-- 
Haiteng Jiang
PhD candidate
Donders Institute for Brain, Cognition and Behaviour
Neuronal Oscillations Group
Computational Cognitive Neuroscience Lab
https://sites.google.com/site/haitengjiang/
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