[FieldTrip] help

[jan-mathijs schoffelen]

Hi Sendy,

You may want to have a look at the following link:

http://fieldtrip.fcdonders.nl/faq/why_does_my_ica_output_contain_complex_numbers?s[]=component

I assume that your data has been passed through the MaxFilter, which massively reduces the rank of your data, causing the ICA algorithm to spit out complex valued numbers.
You need to reduce the rank of your data prior to running the component decomposition, to be less that then true rank in your data.

Best
Jan-Mathijs

On Nov 8, 2013, at 10:47 AM, Sendy Caffarra wrote:

> Hi,
> 
> 
> I'm using Fieldtrip to analyze my Meg data.
> Actually, I'm trying to reject ocular artifacts by using ICA.
> I decreased the sample rate to 300 and I performed the ICA analysis as following:
> 
> cfg = [];
> cfg.resamplefs = 300;
> cfg.detrend    = 'no';
> data_1_rspl = ft_resampledata(cfg, data_1);
> %ICA
> cfg            = [];
> cfg.method = 'runica';
> comp           = ft_componentanalysis(cfg, data_1_rspl);
> 
> 
> It worked, but now when I try to visualize the different ICA components using:
> 
> cfg                 = [];
> cfg.layout          = 'neuromag306mag.lay'; % specify the layout file that should be used for plotting
> cfg.viewmode        = 'component';
> ft_databrowser(cfg, comp);
> 
> I can see how the waves look like, but I cannot see the topographic distribution of them.
> 
> And Matlab gives me this error:
> 
> ??? Error using ==> surf at 78
> X, Y, Z, and C cannot be complex.
> 
> Error in ==> ft_plot_topo at 251
>  h = surf(Xi-deltax/2,Yi-deltay/2,zeros(size(Zi)), Zi, 'EdgeColor', 'none', 'FaceColor',
>  shading);
> 
> Error in ==> ft_databrowser>redraw_cb at 1850
>      ft_plot_topo(chanx, chany, chanz, 'mask', ...
> 
> Error in ==> ft_databrowser at 671
> redraw_cb(h);
> 
> 
> Could you help me in solving this problem?
> I also downloaded the latest version of fieldtrip but it still does not work.
> 
> Thanks for your help.
> 
> Sendy
> 
> 
> Sendy Caffarra
> Postdoctoral researcher BCBL
> www.bcbl.eu
> 
> _______________________________________________
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
> http://mailman.science.ru.nl/mailman/listinfo/fieldtrip

Jan-Mathijs Schoffelen, MD PhD 

Donders Institute for Brain, Cognition and Behaviour, 
Centre for Cognitive Neuroimaging,
Radboud University Nijmegen, The Netherlands

Max Planck Institute for Psycholinguistics,
Nijmegen, The Netherlands

J.Schoffelen at donders.ru.nl
Telephone: +31-24-3614793

http://www.hettaligebrein.nl

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