[FieldTrip] Permutation test design matrix for grand-averaged ERPs

Kate Stone katemsto at gmail.com
Tue Oct 23 17:21:22 CEST 2018

Hi again,

Further to the below, what I would actually prefer to do is use the
depsamplesT test on my data structure containing averages over trials for
each subject (i.e. the output of ft_timelockanalysis).

But every time I try, I get the message "length of the design matrix (2)
doesn't equal the number of observations (694)" - no matter what the
dimensions of the design matrix are. I've set up the matrix exactly as
specified in the tutorial (relevant to my data of course). Any idea what
this error is about?

Thanks again,

On Tue, Oct 23, 2018 at 2:04 PM Kate Stone <katemsto at gmail.com> wrote:

> Hi all,
> I've been following the tutorial here to do a time-locked perm test on ERP
> data: www.fieldtriptoolbox.org/tutorial/cluster_permutation_timelock
> I have computed grand averages for my two conditions and am using
> indepsamplesT with ft_timelockstatistics(cfg, GA_1, GA_2).
> But what should the design matrix be? The example in the tutorial doesn't
> apply as I am using grand averages and the reference for
> ft_timelockstatistics doesn't mention the design matrix, although it is
> definitely required. I have tried design = [1,2], but this doesn't seem to
> give sensible results.
> Thanks in advance,
> Kate

Kate Stone
PhD candidate
Vasishth Lab | Department of Linguistics
Potsdam University, 14467 Potsdam, Germany
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