[FieldTrip] different frequency bins

[Johanna Fieß]

Dear all, 

whenever I try to compute the statistics for (MEG) time-frequency data, this error message comes up:

computing statistic over the frequency range [8.000 11.000]
computing statistic over the time range [0.300 1.100]
Error using ft_appendfreq (line 250)
the input data structures have non-unique frequency bins, concatenation across frequency is not possible

Error in ft_appendfreq (line 139)
      freq = ft_appendfreq(tmpcfg, varargin{:});

Error in ft_freqstatistics (line 231)
    data = ft_appendfreq(cfg, varargin{:});

Out of 35 participants in total, (only) three show slightly different frequency bins (starting point 2.0001 instead of 1.9998) – if I remove them from the average, the error message disappears.
If renaming the freq-structure of those three participants, the error message disappears, too.

Could anyone tell me what causes this problem or how I should handle it?

Thanks a lot in advance!

Johanna


PS: I'm running Matlab R2012b & fieldtrip-20130515
	
		%% stats
		design=[1:10,1:10; ones(1,10),ones(1,10)*2]; 

		cfg = [];
		cfg.frequency       	= 	 [8 11]; 
		cfg.latency        	= 	 [.3 1.1];    
		cfg.method          	= 	'montecarlo';
		cfg.statistic       	= 	'indepsamplesT'; 
		cfg.correctm        	= 	'cluster';
		cfg.clustertail     	=	 0;
		cfg.clusteralpha   	= 	0.05;
		cfg.clusterstatistic = 'maxsum';
		cfg.numrandomization = 500;
		cfg.alpha           	 = 	0.05;

		cfg.avgoverfreq     = 'yes';
		% cfg.avgovertime     = 'yes';
		cfg.design         	 = design;
		cfg.neighbours      = neighbours; 
		cfg.ivar 			 = 2;


		stat = ft_freqstatistics (cfg,patUr{:}, konUr{:});  
		cfg = [];
		cfg.alpha  = 0.3;
		cfg.parameter = 'stat';
		cfg.zlim   = [-3 2];
		cfg.layout = '4D148.lay';
		ft_clusterplot(cfg, stat);



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