[FieldTrip] Query regarding extraction of amplitude and latency

[Tineke Snijders]

Hi Mathew,

For extracting amplitude values from a pre-specified time-window you can also use ft_selectdata to select means over a specific time-window / channels (or frequency).

E.g.
cfg=[];
cfg.channel={'F7','F3','FC5'}; %adjust to electrodes of interest, can also be 'all'
cfg.avgoverchan='yes';
cfg.avgovertime='yes';
cfg.latency=[0.3 0.5];
Avg300500_grand_erpLF=ft_selectdata(cfg,grand_erp);

You can do that on individual ERPs or on grand averages (with keepindividual='yes'), and then you can save the relevant numbers to a file using standard matlab code as Jan-Mathijs suggested.

Kind regards,

Tineke


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Today's Topics:

   1. European Society for Cognitive and Affective Neuroscience -
      May 2024 - Ghent, Belgium (CASPAR Emilie)
   2. Normalization of timelocked average LFP amplitude (voltage)
      (Zheng, Ning)
   3. Re: Query regarding extraction of amplitude and latency
      values (Varghese Mathew 1881002)


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Message: 3
Date: Fri, 12 Jan 2024 09:11:10 +0530
From: Varghese Mathew 1881002
	<varghese.mathew at res.christuniversity.in>
To: FieldTrip discussion list <fieldtrip at science.ru.nl>
Subject: Re: [FieldTrip] Query regarding extraction of amplitude and
	latency values
Message-ID:
	<CAFnh8hJPVj62qZfiXTRpsebaKFvJnojEhh0dBvs0OYxPodRBow at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Thank you for the reply. This gave me good clarity.

Sincerely
Varghese Mathew

On Wed, Jan 3, 2024 at 3:32 PM Schoffelen, J.M. (Jan Mathijs) via fieldtrip <fieldtrip at science.ru.nl> wrote:

> Hi Mathew,
>
> If you want to extract amplitude values from a pre-specified time 
> window, I would just compute the average ‘by hand’, i.e. take the mean 
> (across the relevant dimension of the matrix) from a subselection of 
> time points. If you want to extract the latency of a peak, and then 
> use the amplitude corresponding to that peak, I would use MATLAB’s 
> findpeaks function (or some other heuristic), and use the amplitude 
> values that correspond to the identified peaks. This requires some 
> ‘plain’ matlab coding, there’s no FieldTrip functionality that gives you such results directly.
>
> Good luck with your analysis,
> Jan-Mathijs
>
>
> On 29 Dec 2023, at 04:30, Varghese Mathew 1881002 via fieldtrip < 
> fieldtrip at science.ru.nl> wrote:
>
> Hi
> I am a Ph.D. scholar working on face processing studies. I am 
> currently trying to use the Fieldtrip toolbox for doing ERP analysis. 
> I am able to plot the ERP and topo plots. I would like to know if 
> there is a way to extract amplitude and latency values from different 
> time windows of interest, to conduct statistical analysis in another software.
> I'm really looking forward to any leads.
>
> Thanks in advance
> --
> Varghese Mathew
> Ph.D Scholar
> CHRIST (Deemed to be university)
> Bangalore-29
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