issues with clusterrandanalysis

[Eric Maris]

Dear Andre,


> As you said, it doesn't look like the neighborhood structure is being
> created properly. I was not able to generate it successfully using the
> following settings:
> cfg.neighbourdist = 4
> cfg.elec = ALLDATA1(1).elec %(with .pnt and .label fields)
> neighbours = neighbourselection(cfg, ALLDATA1(1).label)
>
> Neighbors becomes a series of 64 structures, but each structure's
> neighblabel field is empty. Perhaps this is also what happens when the
> script tries to generate the neighbourhood structure.


1. Are the labels is elec.label and ALLDATA1(1).label identical?
2. Are the electrode positions in elec.pnt expressed on the proper scale
(i.e., such that cfg.neighbourdist makes sense)?


If these checks don't help, send me you one of your data structures
(maris at nici.ru.nl).

Good luck,

Eric

>
> Thanks for your help,
>
> Andre
>
>
>
>
> -----Original Message-----
> From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On
Behalf
> Of Eric Maris
> Sent: Monday, April 09, 2007 3:11 AM
> To: FIELDTRIP at NIC.SURFNET.NL
> Subject: Re: [FIELDTRIP] issues with clusterrandanalysis
>
> Dear Andre,
>
>
>
> > I am beginning to use the clusterrandanalysis function, but have not
been
> > finding any significant clusters in my EEG data. I changed alpha and
> > alphathresh to be 0.5, but this still didn't produce any results
> > (posclusters and negclusters are both empty). To test whether the config
> > settings were actually working, I generated some random time frequency
> data
> > using the following commands:
> >
> > s = size(TFR.powspctrm (s is 17 trials by 64 channels by 40 freqs by 99
> time
> > steps)
> > rpow = rand(s); (produces pseudorandom nums between 0 and 1)
> > TFR.powspctrm = rpow;
> >
> > I reran clusterrandanalysis with this new TFR, but still got no
clusters.
> > This puzzles me, because a random series of numbers should be
> statistically
> > different from physiologically produced spectral data.
>
>
> My first guess is that there is something wrong with your neighborhood
> structure. Can you send me a copy of the screen output (only the part
before
> the counting of the randomizations)?
>
> When using MEG-data coming from a  CTF system, this neighborhood structure
> is calculated automatically. However, I guess you are using a different
> sensor configuration. In that case, you have to supply this information to
> clusterrandanalysis. You can find more information about this in the
online
> help of clusterrandanalysis.
>
>
> Kind regards,
>
> Eric
>
>
>
> >
> > I used the basic config settings found in the tutorial, which were:
> >
> >   cfg.statistic = 'indepsamplesT';
> >   cfg.alphathresh = 0.5;
> >   cfg.makeclusters = 'yes';
> >   cfg.minnbchan = 2;
> >   cfg.clusterteststat = 'maxsum';
> >   cfg.onetwo = 'twosided';
> >   cfg.alpha = 0.5;
> >   cfg.nranddraws = 100;
> >   cfg.channel = 'all';
> >   [clusrand] = clusterrandanalysis(cfg, TFR1, TFR2);
> >
> > Any ideas what I am doing wrong?