[FieldTrip] Help with definetrial for EGI .mff file

[Varghese Mathew 1881002]

Thank you so much for the response.
I have tried using ft_trialfun_general in the following code
datapath='E:\FT\OFP1.mff'
EGIformat= 'egi_mff_v3'
cfg = [];
cfg.dataset = datapath;
cfg.dataformat = EGIformat
cfg.headerformat = EGIformat
cfg.trialdef.eventtype = 'stim';
cfg.trialdef.prestim = 1;
cfg.trialdef.poststim =1;
cfg.trialdef.eventvalue = {'01''02''03''04'};
cfg.trialfun = 'ft_trialfun_general';
cfg = ft_definetrial(cfg)

I am getting a following response

Error using ft_definetrial
no trials were defined, see FT_DEFINETRIAL for help

This made me think if I should change the trialfun_general. Is there
something I have missed and also is there any standard format to define
trials on Netstation files (.mff)?

Thank you again for the response.

Sincerely
Varghese Mathew


On Wed, Apr 19, 2023 at 11:12 PM Schoffelen, J.M. (Jan Mathijs) via
fieldtrip <fieldtrip at science.ru.nl> wrote:

> Hi Mathew,
>
> I am a bit surprised that you think that you need to adjust the
> ft_trialfun_general. The idea is that this function is quite generic, and
> given the scenario that you sketch, you probably don’t need to change any
> fieldtrip function. The partial error that you report is difficult to
> evaluate, since it’s only partial. Right now it’s just random guessing as
> to what might be going on. The error looks as if MATLAB tries to access a
> structure’s field called headerfile, but for some reason in does not exist
> in the struct that it is evaluating.
>
> for instance, if you define on the matlab command line the following
> struct:
>
> x.a = 1;
>
> and then query x.b, you get the error you report.
>
> What is the full error stack, i.e. which line in which matlab function is
> throwing the error?  And what is the code that you try to execute (i.e. the
> specification of the cfg, and the fieldtrip function you are calling).
>
> Good luck,
> Jan-Mathijs
>
>
> On 19 Apr 2023, at 16:27, Varghese Mathew 1881002 via fieldtrip <
> fieldtrip at science.ru.nl> wrote:
>
> Hi
> I am doing analysis on Netstation EGI .mff file using Fieldtrip, I have
> tried using .mff file directly and after converting to EDF. However, I am
> getting error in defining trials. Mostly I get an error message  Unrecognized
> field name "headerfile"  .
> I would like to know how to go about this in EDF or .mff format.
> It will also be helpful if someone can help with how to modify
> ft_trialfun_general for .mff file as well.
> I am pasting the code I used, below.
> cfg=[]
> cfg.dataset = 'E:\FT\OP17.mff';
> cfg.dataformat = 'egi_mff_v3'
> cfg.headerformat = 'egi_mff_v3'
> cfg.trialdef.eventtype = 'stim';
> cfg.trialdef.prestim = 1;
> cfg.trialdef.poststim =1;
> cfg.trialdef.eventvalue = {'01''02''03''04'};
> cfg.trialfun = 'ft_trialfun_general_stimmod';
> cfg = ft_definetrial(cfg)
>
>
> For modifying trialfun_general
>
> function [trl, event] = ft_trialfun_general_stimmod(cfg)
> event = ft_read_event(cfg.dataset, 'headerformat', 'egi_mff_v3');
> % Find trigger values
> trigger = [event(strcmp('stim', {event.type})).value]';
> % Note: Replace 'STI101' with the label of the trigger channel that
> % contains the trigger values for your data
> % Define trial segments
> trl = [];
> for j = 1:length(trigger)
> if any(trigger(j) == [01 02 03 04])
> trlbegin = event(j).sample;
> trlend = trlbegin + 1000; % define trial length as 1 second
> offset = 0; % no offset
> newtrl = [trlbegin trlend offset trigger(j)];
> trl = [trl; newtrl];
> end
> end
> Please help with the issue, as I am trying to pick up analysis using
> Fieldtrip and I do not have a coding background.
> Looking forward for a response,
>
> Sincerely
> --
> Varghese Mathew
>
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-- 
Varghese Mathew
Mobile No. 9535395896
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