[FieldTrip] channelrepair issue

[Jim Li]

Hi Jan-Mathijs,

>From Fieldtrip data structure I saw that the coordinate of A234 is [
-7.2133    9.1712    5.7117]. And it's [14.4320   -0.0683    0.4437]
for A121. All these are in "cm". So the distance between the two channels
are  24.1172cm.

I checked 4D's orignial file and found the channel coordinates to agree with
what I read from Fieldtrip. So I'm wondering how those coils 24.1172cm apart
can be considered neighbours (within 4cms).

Thanks a lot,

Jim


On Thu, Jun 30, 2011 at 1:50 AM, jan-mathijs schoffelen <
jan.schoffelen at donders.ru.nl> wrote:

> Hi Jim, where exactly are they located with respect to the bad channel?
>
> Best,
>
> Jan-Mathijs
>
>
>   On Jun 30, 2011, at 8:05 AM, Jim Li wrote:
>
>   Dear all,
>
> We have 4D's WH3600 MEG system (248 channels) and we found the
> -----------------
>
> cfg = [];
>
> cfg.dataset =
> 'e,rfhp0.1Hz';
>
> cfg.trialdef.eventtype = 'TRIGGER';
>
> cfg.trialdef.eventvalue = 320;
>
> cfg.trialdef.prestim = 1;
>
> cfg.trialdef.poststim = 1
> ;
>
> cfg = ft_definetrial(cfg);
>
> cfg.blc =
> 'yes';
>
> cfg.blcwindow = [-1 0];
>
> cfg.channel = {'MEG'};
>
> raw_DATA = ft_preprocessing(cfg);
>
> raw_DATA.grad = ft_convert_units(raw_DATA.grad, 'cm')
>
> cfg = [];
> cfg.badchannel = {'A234'};
> [raw_DATA] = ft_channelrepair(cfg, raw_DATA)
> the input is raw data with 248 channels and 201 trials
> repairing channel A234
>   using neighbour A121
>   using neighbour A143
>   using neighbour A154
>   using neighbour A173
>   using neighbour A224
>   using neighbour A8
>   using neighbour A91
> repairing bad channels for trial 1
> repairing bad channels for trial 2
> repairing bad channels for trial 3
> ...
> ------------------------------------
>
> But channels like A121 and A143 are far away from the bad channel A234. How
> can they be used as neighbours (i.e. within 4cm, the default value for
> cfg.neighbourdist) for this bad channel?
>
> Any suggestions?
>
> Thanks a lot.
>
> Jim
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip
>
>
>   Dr. J.M. (Jan-Mathijs) Schoffelen
> Donders Institute for Brain, Cognition and Behaviour,
> Centre for Cognitive Neuroimaging,
> Radboud University Nijmegen, The Netherlands
> J.Schoffelen at donders.ru.nl
> Telephone: 0031-24-3614793
>
>
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> fieldtrip at donders.ru.nl
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>
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