[FieldTrip] Data structure for within-UO designs

[Ward, E.G.E. (Emma)]

Dear Umberto,

I think the optimal organisation would be one variable per condition, or perhaps a structure with one cell per condition (might be easier to keep organised when you have so many conditions), and within each of those cells, the averaged data per participant for that condition.

So you would have a structure containing 12 cells, one for each condition, and in each of those cells you would have 30 cells, each with the output from ft_timelockanalysis, which I think has fields label, fsample, avg, time, dimord, cfg and grad. This you don't have to do yourself, those are the automatic output fields from that function.

Is this what you wanted to know?

Best wishes,

Emma Ward, MSc
Postdoctoral Researcher
Freie Universitaet Berlin

e-mail: e.ward at donders.ru.nl
website: https://sites.google.com/view/emma-k-ward

________________________________________


Message: 3
Date: Mon, 12 Apr 2021 15:21:45 +0000
From: "Cavallo, Umberto (Stud. FPN)"
        <u.cavallo at student.maastrichtuniversity.nl>
To: FieldTrip discussion list <fieldtrip at science.ru.nl>
Subject: [FieldTrip] Data structure for within-UO designs.
Message-ID: <1618240905335.40242 at student.maastrichtuniversity.nl>
Content-Type: text/plain; charset="iso-8859-1"

Dear all,

I am an msc student and I am currently analysing eeg 64 channels data.

Particularly, i have a within subject design in which i have 12 conditions of interest and 30 subjects.

I am planning to do a cluster based permutation t-test, which i successfully carried out on a single participant (pilot data), however soon i will have to analyse data from 30 participants.

I have read all the tutorials pertaining this argument but i could not find the ERF_orig.mat file in the FTP server.

Thus, i wanted to ask you specifically about the data structure contained in that file.

Quoting from the "cluster-based permutation tests on event related fields"


"the timelock structures containing the event-related averages of all subjects.

ERF_orig contains allsubjFIC and allsubjFC, each storing the event-related averages for the fully incongruent, and the fully congruent sentence endings, respectively.

The format for these variables, are a prime example of how you should organise your data to be suitable for ft_XXXstatistics. Specifically, each variable is a cell-array of structures, with each subject's averaged stored in one cell. To create this data structure two steps are required. First, the single-subject averages were calculated individually for each subject using the function ft_timelockanalysis<https://github.com/fieldtrip/fieldtrip/blob/release/ft_timelockanalysis>. Second, using a for-loop we have combined the data from each subject, within each condition, into one variable (allsubj_FIC/allsubj_FC). We suggest that you adopt this procedure as well."


Now my question regards the timelock structure. How should it be organized and which fields should it contain?

Should it be obtained by specifying cfg.keeptrials?

Actually just having a look at the structure organization would solve my problem.


Thanks all for your time,

Best,

Umberto?

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