Eric Maris maris at NICI.RU.NL
Wed Nov 1 10:19:24 CET 2006

Dear Hanneke,

> -----Original Message-----
> From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On
Behalf Of
> Hanneke van Dijk
> Sent: Wednesday, November 01, 2006 9:54 AM
> Subject: [FIELDTRIP] Clusterrandanalysis
> Dear all,
> I have been working with clusterrandanalysis a while ago and started the
> same scripts this week, but I don't seem to be able to replicate my
> results. Has something been changed in the function? If yes, how can I
> that?

I have discussed this with Vladimir Litvak in a
non-discussion-list-correspondence. The non-reproducibility is due to an
error in the old code (not serious, however). Here is an excerpt from an
email to Vladimir that may clarify things:

With respect to the non-reproducibility of your old result, the cause of the
problem lies in the private subfunction findcluster.m. In the old version of
findcluster.m (the one you used for your first analyses), the pruning of
significant (sensor, frequency)-pairs, as controlled by cfg.minnbchan, was
performed incorrectly. This has no consequence for false alarm rate control,
because the pruning is part of the procedure for calculating the overall
test statistic (i.e., the maximum cluster-level statistic), and the
nonparametric test controls the false alarm rat for all test statistics.

You will get your old result with the latest FT version if you replace
cfg.minnbchan=2 by cfg.minnbchan=1. The error in the old version of
findcluster.m was that the number of neighboring significant (sensor,
frequency)-pairs was calculated incorrectly for symmetric neighbourhood
structures. So, when reporting about your results, you have to change
nothing, except that you may mention that the option cfg.minnbchan=1 was

Good luck,


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