[FieldTrip] ft_timelockgrandaverage with trials

[Stephen Politzer-Ahles]

Hi Mary-Jo,

Are you sure you need individual trials? Normally, for a group-level
comparison of means, the unit of observation would be the subject-wise
averages, rather than all the trials; as far as I can think of, the only
time you would want individual trials for timelock statistics would be if
you are doing analysis on a single participants (like in the example at
http://www.fieldtriptoolbox.org/tutorial/cluster_permutation_timelock#between-trials_experiments)
or if you are computing event-related regression coefficients rather than
event-related averages. Can you give more detail about what you're trying
to do, what code you used to try running your statistics, and what error
you got?

Best,
Steve



---
Stephen Politzer-Ahles
University of Oxford
Language and Brain Lab
Faculty of Linguistics, Phonetics & Philology
http://users.ox.ac.uk/~cpgl0080/



> Message: 4
> Date: Wed, 24 Feb 2016 10:01:04 +0000
> From: "Diepeveen, Mary-Jo" <Mary-Jo.Diepeveen at mpi.nl>
> To: "fieldtrip at science.ru.nl" <fieldtrip at science.ru.nl>
> Subject: [FieldTrip] ft_timelockgrandaverage with trials
> Message-ID:
>         <9AEBC8200222F443B6E297F0D479F1311C486C5A at UM-EXCDAG-A03.um.gwdg.de
> >
> Content-Type: text/plain; charset="us-ascii"
>
> Hello all,
>
> I have done an EEG study in which I have four conditions per subjects and
> two different subject groups. I would now like to compare the same
> condition between the two subject groups. To do this, I first tried
> ft_timelockanalysis with cfg.keeptrials=' yes'  after which I tried to do
> ft_timelockgrandaverage. I get the following message: Warning depreciating
> trial field using the avg to compute the grand average (bug2372). After
> some googling I found an old post saying that ft_timelockgrandaverage does
> not support input data with "trial" field, meaning then that what I am
> trying to do is not possible. Trying to do the statistics after anyways
> also did not work because I need the .trial field. The post I found is
> however, from 2014 so I was wondering if this problem is fixed now. I have
> thought of my own way around this, but I was wondering if you maybe have
> any ideas too.
>
> Thanks!
>
> Mary-Jo
>
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