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<font size="2" face="Dialog">Hi Michael,</font> </p>
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<font size="2" face="Dialog">thanks a lot for your response. Yes, I kept everything the same, the only difference beeing the Matlab path pointing to the old vs new FT version. I will keep on searching for a possible flaw in my code and will tell so if I found one.</font> </p>
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<font size="2" face="Dialog">Thanks again, best regards,</font> </p>
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<font size="2" face="Dialog">Gregor</font> </p>
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<font face="Dialog" STYLE="font-size: 10pt"><br>--
<BR>Dr. rer. nat. Gregor Volberg <gregor.volberg@psychologie.uni-regensburg.de> ( mailto:gregor.volberg@psychologie.uni-regensburg.de )
<BR>University of Regensburg
<BR>Institute for Experimental Psychology
<BR>93040 Regensburg, Germany
<BR>Tel: +49 941 943 3862
<BR>Fax: +49 941 943 3233
<BR><a href="http://www.psychologie.uni-regensburg.de/Greenlee/team/volberg/volberg.html
">http://www.psychologie.uni-regensburg.de/Greenlee/team/volberg/volberg.html
</a><BR><br><br></font>>>> "Michael Wibral" <michael.wibral@web.de> 11/3/2011 4:57 PM >>><br>Hi Gregor,<br><br>in principle the first level statistics that determine cluster membership (and thereby cluster shapes etc.) can also vary from one set of permutations to the next, esp. on the borders of a cluster (this is why it is typically said that the localization of a cluster is not as trustworthy as its existence). Other resaons for differences are differing number of permutations - did you set everything the same?<br><br>This said there might well be another problem - I hope the cluster people can have a look into it.<br><br>Best ,<br>Michael<br><br><br> </p>
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<b>Von:</b> "Gregor Volberg" <Gregor.Volberg@psychologie.uni-regensburg.de><br><b>Gesendet:</b> Nov 2, 2011 6:34:43 PM<br><b>An:</b> fieldtrip@donders.ru.nl<br><b>Betreff:</b> [FieldTrip] Wrong clustering of electrodes in newer FT versions?<br><br> </p>
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<font size="2" face="Dialog">Dear fieldtrip community,</font> </p>
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<font size="2" face="Dialog">I just encountered an unexpected behavior of FT that I would like to share with the list. It is that the cluster permutation test formed incorrect clusters from a given set of significant electrodes in newer FT versions (ft-20111012; I also tried with ft-20111028). </font> </p>
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<font size="2" face="Dialog">For example, when using an old ft version (ft-20100810) and freqstatistics I get a negative cluster with 17 contiguous electrodes. With the newer ft version, using the same data and the same cfg, three significant electrodes that are spatially contiguous to the other significant electrodes are not included in the cluster. Also, three electrodes that are spatially seperated and are actually part of the first cluster are grouped into a separate cluster. I attached a picture with the respective clusterplots where differences are marked with red arrows.</font> </p>
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<font size="2" face="Dialog">I am aware that the permutation p-value for a given cluster can be different in two separate analyses, but the grouping of significant electrodes into clusters should always be the same, am i right? I double-checked the cfg.neighbours, after conversion to new 'struct' style, and they were identical in the "old ft" and "new ft" analysis. Also, the stat.stat field and the stat.cfg.clustercritval were the same for both analyses. Thus, the same neighbourhood relations and the same significant electrodes should be used for grouping. Yet I get different results... </font> </p>
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<font size="2" face="Dialog">I am almost sure that this is trivial, but I could not yet replicate my old results with new FT and this makes me nervous. Has someone made a similar experience? Or do newer versions of ft use some further information besides cfg.neighbours for clustering, somewhere in the *cfg.previuous perhaps, that I am not aware of? Any comments are highly welcome.</font> </p>
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<font size="2" face="Dialog">Best regards,</font> </p>
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<font size="2" face="Dialog">Gregor</font> </p>
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<font size="2" face="Dialog">cfg = [];</font> </p>
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<font size="2" face="Dialog">cfg.neighbours = neighbours;</font> </p>
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<font size="2" face="Dialog">cfg.minnbchan=1;</font> </p>
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<font size="2" face="Dialog">cfg.avgoverfreq = 'yes';</font> </p>
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<font size="2" face="Dialog">cfg.avgovertime = 'yes';</font> </p>
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<font size="2" face="Dialog">cfg.method = 'montecarlo';</font> </p>
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<font size="2" face="Dialog">cfg.correctm = 'cluster';</font> </p>
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<font size="2" face="Dialog">cfg.statistic = 'depsamplesT';</font> </p>
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<font size="2" face="Dialog">cfg.tail = 0;</font> </p>
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<font size="2" face="Dialog">cfg.alpha = 0.05;</font> </p>
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<font size="2" face="Dialog">cfg.clusteralpha = 0.05;</font> </p>
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<font size="2" face="Dialog">cfg.numrandomization = 1000;</font> </p>
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<font size="2" face="Dialog">cfg.design = [[1:14 1:14]; [zeros(1,14)+1 zeros(1,14)+2]];</font> </p>
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<font size="2" face="Dialog">cfg.uvar = 1;</font> </p>
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<font size="2" face="Dialog">cfg.ivar = 2;</font> </p>
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<font size="2" face="Dialog">cfg.latency = [2.24 2.53];</font> </p>
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<font size="2" face="Dialog">cfg.frequency = [17 21];%</font> </p>
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<font size="2" face="Dialog">stat = ft_freqstatistics(cfg, DC, TC);</font> </p>
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<SPAN STYLE='style="font-size: 10pt" FONT-SIZE:"10pt" ;FONT-FAMILY:"Dialog"'>--<br style="font-family: Dialog; font-size: 10pt">Dr. rer. nat. Gregor Volberg <gregor.volberg@psychologie.uni-regensburg.de> ( mailto:gregor.volberg@psychologie.uni-regensburg.de )<br style="font-family: Dialog; font-size: 10pt">University of Regensburg<br style="font-family: Dialog; font-size: 10pt">Institute for Experimental Psychology<br style="font-family: Dialog; font-size: 10pt">93040 Regensburg, Germany<br style="font-family: Dialog; font-size: 10pt">Tel: +49 941 943 3862<br style="font-family: Dialog; font-size: 10pt">Fax: +49 941 943 3233<br style="font-family: Dialog; font-size: 10pt"><a href="http://www.psychologie.uni-regensburg.de/Greenlee/team/volberg/volberg.html
">http://www.psychologie.uni-regensburg.de/Greenlee/team/volberg/volberg.html </a></SPAN><br><br>
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