[FieldTrip] Stats matrix incomplete - cluster-based permutation test

Anne Mickan amickan1990 at gmail.com
Thu Dec 10 18:14:10 CET 2015


Dear all,

I'm just starting to work on a cluster-based permutation test script based
on the tutorial for within-subject designs on the fieldtrip website. I ran
into an issue when computing the [stat] matrix. I used the code as it was
on the website:

[stat] = ft_timelockstatistics(cfg, Correct{:}, Incorrect{:});

with the Correct and Incorrect matrices looking as follows:

Correct{1}

        avg: [34x600 double]
       time: [1x600 double]
    fsample: '500'
      label: {34x1 cell}
     dimord: 'chan_time'
        dof: [34x600 double]
        var: [34x600 double]

The function runs without problems, i.e I don't get any error messages.
However, the result seems incomplete.

stat =
                   prob: [25x1 double]
            posclusters: []
    posclusterslabelmat: [25x1 double]
        posdistribution: [1x500 double]
            negclusters: [1x1 struct]
    negclusterslabelmat: [25x1 double]
        negdistribution: [1x500 double]
                cirange: [25x1 double]
                   mask: [25x1 logical]
                   stat: [25x1 double]
                    ref: [25x1 double]
                 dimord: 'chan_time'
                  label: {25x1 cell}
                   time: 0
                    cfg: [1x1 struct]

Specifically, I later run into trouble with the stat.posclusterslabelmat
and stat.negclusterslabelmat matrices which should apparantly contain far
more values something more like 25x500 instead of 25x1. When calling
neg_int = all(neg(:, m(k):m(k+1)), 2)
I get the "Index exceeds matrix dimensions" error message which I assume
has to do with the fact that "neg" does not have the appropriate matrix
dimensions
(neg = ismember(stat.negclusterslabelmat, neg_signif_clust); )

Where is the error / where should I look for the error?

Some further design details:
Nsubj = 24
2 conditions = Correct, Incorrect
Within-subject design
sampling rate = 500
34 channels

I hope I gave enough / the necessary information for someone to help me
out.

Thanks in advance!

Best,
Anne
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