[FieldTrip] beamformer_sam lambda

[jan-mathijs schoffelen]

Dear Don,

At first sight, this makes sense to me, also in the light of consistency across the different algorithms. I'll create a 'bug' out of this and we will discuss it in the group and most likely implement it.

Thanks for the notification and best wishes,

Jan-Mathijs


On Jan 6, 2012, at 10:12 PM, Rojas, Don wrote:

> To all,
> 
> I encountered a problem with the 'sam' method for ft_sourceanalysis. It looks to me that when specifying the configuration option:
> 
> cfg.sam.lambda = '5%';
> 
> i.e., lambda is a percentage, not an actual number, the beamformer_sam routine does not have comparable code as the beamformer_lcmv routine to handle that type of input. I'm wondering if simply inserting the following bit of code between lines 97 and 99 of beamformer_sam, borrowed and edited from beamformer_lcmv, will work:
> 
> if ~isempty(lambda) && ischar(lambda) && lambda(end)=='%'
>   ratio = sscanf(lambda, '%f%%');
>   ratio = ratio/100;
>   lambda = ratio * trace(all_cov)/size(all_cov,1);
> end
> 
> This seems to work okay in limited tests, but maybe I'm making a mistake here. I'm using a recent svn code version, revision 5097.
> 
> Best,
> 
> Don
> 
> 
> -----------------------
> Don Rojas, Ph.D.
> Associate Professor of Psychiatry
> U. of Colorado Denver Anschutz Medical Campus
> Director, UCD Magnetoencephalography Lab
> 13001 E. 17th Pl F546
> Aurora, CO 80045
> 303-724-4994
> 
> _______________________________________________
> 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

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