[FieldTrip] freqstatistics with sbj_chan_freq (Vit?ria Piai)

[Haiteng Jiang]

Hi Viotira,
   If you don't care about time information , you can average  it by
specifying cfg.avgovertime = 'yes' on the TFR , then the cluster will be
formed in channel-frequency format.  If you use  mtmfft , you should
pre-select effect interval .   Otherwise,   it could be not consistent .
                                                                       Best,

 Haiteng







> Message: 1
> Date: Sun, 13 Apr 2014 18:53:10 -0700
> From: Vit?ria Piai <v.piai.research at gmail.com>
> To: FieldTrip discussion list <fieldtrip at science.ru.nl>
> Subject: [FieldTrip] freqstatistics with sbj_chan_freq
> Message-ID: <534B3F86.9070904 at gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
>
> Hi all,
>
> I'm kinda stuck not being able to figure out what's going wrong with my
> freqstats, so I thought I could share it here and see if anyone can see
> where I'm going wrong.
> When I run freqstatistics on TFRs, I get a negative cluster (p = .001)
> between 8 and 25 Hz with the topography very similar to the one in the
> figure. But I just want non-time-resolved spectra.
> So I have power spectra calculated with mtmfft (dpss tapers) between 1
> and 50 Hz (5 Hz smoothing) and this is the one for which I've been
> trying to run freqstatistics, unsuccessfully.
> I'm using a pretty standard cfg for freqstats (basically, the same I use
> for the TFRs, which give me the negative cluster with p =.001) and the
> data in the comparison are structured as sbj_chan_freq. With this
> time-unresolved data, only posclusters are detected, with ps > .4! If I
> plot the stat output, it has the exact same negative cluster as I get
> for the TFRs (see Figure), and as far as I can see, no real positive
> cluster, but the function doesn't even detect any negative clusters.
> I must be doing something wrong because the time-resolved and
> -unresolved effects are pretty much the same in the descriptives. I
> remember running stats on time-unresolved data before and getting a
> reasonable output, so I guess my ft_freqstatistics isn't working well
> right now. I just can't figure out why.
> Does anyone have any tips for how I could go about to find out why the
> negative clusters are being disregarded?
>
> Thanks a lot, Vit?ria
>
-- 
Haiteng Jiang
PhD candidate
Neuronal Oscillations Group
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognitive Neuroimaging
Radboud University Nijmegen

Visiting address
Room 2.32
Donders Centre for Cognitive Neuroimaging
Kapittelweg 29
6525 EN  Nijmegen
the Netherlands

 Tel.: +31 (0)243668291
 Web:  https://sites.google.com/site/haitengjiang/
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