Within-subject coherence statististics for virtual sources

Lorina Naci lorina_naci at YAHOO.CO.UK
Mon Jan 8 17:33:44 CET 2007

Dear Jan Mathijs and co,
  thank you for your previous reply. After several trials, i was able to run the script; the problem seems to have something to do with the space and resources allocated to the user on our server.

  I am able to get probabilities of coherence (for my subject group) for each channel, time and frequency bins. I just wanted to check that I am reading the probabilities correctly: even thought the statistic test is non parametric, significant differences are denoted by probability values of <0.05? Is this right?

  Many thanks again - it is very exciting to have group data coherence results,

Jan Mathijs Schoffelen <Jan.Schoffelen at FCDONDERS.RU.NL> wrote:
        v\:* {behavior:url(#default#VML);}  o\:* {behavior:url(#default#VML);}  w\:* {behavior:url(#default#VML);}  .shape {behavior:url(#default#VML);}        st1\:*{behavior:url(#default#ieooui) }                Dear Lorina,

  My outlook blocked your attached data. I managed to get it anyhow and ran your script. It runs through just fine. Apparently FT is doing what it should do.

  Yours, JM


  From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On Behalf Of Lorina Naci
Sent: Friday, December 08, 2006 1:01 PM
Subject: Re: [FIELDTRIP] Within-subject coherence statististics for virtual sources

    Dear Jan Mathijs and co,

thanks for following up with my queries. I feel very close to getting my result barring a few difficulties.

      > From the other statfun_xxx functions in the fieldtrip ‘private’
> folder, I thought that the statfun_depsamplesT would be more
> appropriate for calculating the t statistic for my two conditions.
> However, when I modify my script by substituting cfg.statistic =
> ‘diff’ for cfg.statistic = ‘depsamplesT’ and run it, it crashes.

could you be a bit more specific about why it crashes? Theoretically it shouldn't crash, but I am not aware of the intricacies of the function.

    I have run the script (attached) several times and get slightly different errors each time. The last error version i get is 'Segmentation violation occurred within signal handler. Unable to complete stack trace; stack was probably corrupted.' Any hints as to what this may mean? I've also attached here my data structures (6 subjects, two conditions (XM, Vis) each), just in case.

    >It might be worthwhile to check whether there is a statfun_paired-tstat in the release-version, >which should do the same trick.

    I did look into the most recent version of Fieldtrip (07.12.2006) and don't think this function is available.

    Many thanks,



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