[Eeglablist] Inquiry about Importing cnt file into MATLAB

[Cedric Cannard]

Hi,

Can you do an average reference and high pass filter at 1 Hz (in Tools menu) and send another screenshot?
Regarding the blank plot, that’s normal, select “remove DC offset” in the plot menu (or after the lowpass filter), and the signal should become visible.

You can also send a link to the file and I’ll take a look.

Cheers,

Cédric

On Tue, Dec 28, 2021 at 08:43, SAMUEL SUI LUNG SZE via eeglablist <eeglablist at sccn.ucsd.edu> wrote:

> Dear all,
>
> Hello, everyone. I would like to ask about importing CNT files. I have
> difficulty importing cnt files "properly" into Matlab. I have tried two
> ways, and I do not seem to do this correctly in either way.
>
> Regarding the *first* way, I go to "File" -> "Import data" -> "Using EEGLAB
> functions and plugins" -> "From Neuroscan .CNT file". For the dialogue
> "Load a CNT dataset", I leave the setting as it is:
>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__drive.google.com_file_d_1JNuprB2ZbHnPFs86qlOIlhBK3opI-5FMXX_view-3Fusp-3Dsharing&d=DwIBaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=smWDMM697QfkjvdeeOoBs51YrNCotHMCj5pnqwkLtVZXsLLNe6bDgd9vWfOhByWk&s=PGA3wKMKQmHZuLQ4qEaskW00YbcG1ni3oEZUMiHVT5Y&e=
>
> On the homepage of EEGLAB, I can see the details of the EEG dataset.
>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__drive.google.com_file_d_1x1iNwWmVFWyk0t6jLfAsShbmiXhjILN7_view-3Fusp-3Dsharing&d=DwIBaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=smWDMM697QfkjvdeeOoBs51YrNCotHMCj5pnqwkLtVZXsLLNe6bDgd9vWfOhByWk&s=C92DgrwgIcm_CHtMFr0P-C5xYIccwaL02OUizfqqF4E&e=
>
> However, when I go to "Plot" -> "Channel data (scroll)", though the
> channels and their labels are shown on the y-axis clearly, I do not see any
> EEG data in the time-domain plot. To be specific, I do not see any
> fluctuation of EEG signals in each channel.
>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__drive.google.com_file_d_10701oAA6UT7-2DMysNbgeCW0onPm1fls2x_view-3Fusp-3Dsharing&d=DwIBaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=smWDMM697QfkjvdeeOoBs51YrNCotHMCj5pnqwkLtVZXsLLNe6bDgd9vWfOhByWk&s=_7OATDvYsD_3U6507SxvGKYB5G6mITaE2lcRTcJaBEE&e=
>
> As for the *second* way, I run the code below to import the EEG dataset
> into Matlab:
>
> EEG1 = pop_loadcnt('/Users/samuelsze/Desktop/L1/Acquisition_practice.cnt' ,
> 'dataformat', 'auto', 'memmapfile', '');
>
> Then, I plot the dataset "EEG1" using the code below,
>
> plot(EEG1.times(:), EEG1.data(:,:))
>
> and the resulting plot is as below:
>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__drive.google.com_file_d_1QJqg4HA5ztwUhtJY2F3RiPLv3GzWSNwy_view-3Fusp-3Dsharing&d=DwIBaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=smWDMM697QfkjvdeeOoBs51YrNCotHMCj5pnqwkLtVZXsLLNe6bDgd9vWfOhByWk&s=8m2-OCvwL_CDFZ9ySMRFhUFbxAGjQ3Q7A1MIxYGOvH0&e=
>
> My gut tells me that I may have used the wrong ways to import the CNT file
> because when I import the same CNT file to, and visualise it on Brainstorm,
> I have a seemingly more reasonable plot:
>
> https://urldefense.proofpoint.com/v2/url?u=https-3A__drive.google.com_file_d_1uZH4kx-2DKkV-5F3oLcsl5OBNhg52jOUXzoJ_view-3Fusp-3Dsharing&d=DwIBaQ&c=-35OiAkTchMrZOngvJPOeA&r=kB5f6DjXkuOQpM1bq5OFA9kKiQyNm1p6x6e36h3EglE&m=smWDMM697QfkjvdeeOoBs51YrNCotHMCj5pnqwkLtVZXsLLNe6bDgd9vWfOhByWk&s=B4UEHAelmvN3FUqXJN1j1Hl4uZkORwIBCd-fP4UTGlA&e=
>
> As I think EEGLAB and ERPLAB are more user-friendly (It is a personal
> preference), I would like to learn from you folks how I can correctly
> import the CNT file into EEGLAB and MATLAB. Could you please help me with
> that? Thank you in advance!
>
> Best regards,
> Samuel
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