[FieldTrip] Quick question about depsamplesregrT

[Lee, Kyoung Eun]

Dear Eelke,

Thank you so much for your kind reply.
If I understood your comment correctly, then a positive cluster means high(1)<low(2)<no(3) and a negative cluster means high(1)>low(2)>no(3), is it right?
Thank you again!

Best,
Kyoungeun

-----Original Message-----
From: fieldtrip <fieldtrip-bounces at science.ru.nl> On Behalf Of Eelke Spaak
Sent: Thursday, July 2, 2020 11:34 AM
To: FieldTrip discussion list <fieldtrip at science.ru.nl>
Subject: Re: [FieldTrip] Quick question about depsamplesregrT

Dear Lee Kyoung Eun,

ft_statfun_depsamplesregrT assigns no special meaning to the values of your regressor, i.e. it uses them exactly as you put in. So, a positive t-statistic reflects a positive regression coefficient, which means the dependent variable is positively associated with the regressor. In your case, if high=1, low=2, no=3, then a negative cluster means no>low>high.

Best,
Eelke

On Wed, 1 Jul 2020 at 12:08, Lee, Kyoung Eun <klee773 at gatech.edu> wrote:
>
> Dear FieldTrip users,
>
>
>
> I have a simple quick question.
>
> Those are my parameters for the clustering permutation test.
>
>
>
> cfg.latency          = 'all';
>
> cfg.channel          = 'all';
>
> cfg.frequency        = 'all';
>
> cfg.avgovertime      = 'no';
>
> cfg.avgoverchan      = 'no';
>
> cfg.avgoverfreq      = 'no';
>
> cfg.method           = 'montecarlo';
>
> cfg.statistic        = 'depsamplesregrT';
>
> cfg.correctm         = 'cluster';
>
> cfg.clusteralpha     = 0.05;
>
> cfg.clusterstatistic = 'maxsum';
>
> cfg.minnbchan        = 1;
>
> cfg.tail             = 0;
>
> cfg.clustertail      = 0;
>
> cfg.alpha            = 0.025;
>
> cfg.numrandomization = 1000;
>
> cfg.parameter        = 'm';
>
>
>
> And this is my design matrix. I only have a within-subject factor (high, low, no).
>
>
>
> subj = 42;
>
> design(1,1:subj) = 1:subj; design(1,subj+1:2*subj)= 1:subj; 
> design(1,2*subj+1:3*subj)= 1:subj;
>
> design(2,1:subj) = 1; design(2,subj+1:2*subj)= 2; 
> design(2,2*subj+1:3*subj)= 3;
>
>
>
> cfg.design = design;
>
> cfg.ivar = 2;
>
> cfg.uvar = 1;
>
>
>
> Then, I ran the freqstatistics like this.
>
>
>
> stat = ft_freqstatistics(cfg, High, Low, No);
>
>
>
>
>
> If I found a significant negative cluster, does it mean there is a linear relationship of “high > low > no” or “no> low>high”?
>
> I always confused about the direction of the effect.
>
>
>
> Thank you so much!
>
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> https://doi.org/10.1371/journal.pcbi.1002202

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