[FieldTrip] ft_sourcestatistics

Stenner, Max-Philipp max-philipp.stenner at med.ovgu.de
Wed Mar 7 18:46:06 CET 2012


Dear fieldtrip users,



I am encountering a problem with ft_sourcestatistics when using output from ft_sourcegrandaverage. My parameter of interest is a logratio: log(mean(moments(time of interest))/mean(moments(baseline))) which I simply named 'pow' to be compatible with ft functions. Apart from this, nothing else deviates from how fieldtrip handles the data/nothing else was changed 'manually'.



The problem arises from the fact that the existence of 10 different subjects in the grandaverage (in the usual 1x10 struct field 'trial') isn't represented in the 'powdimord' field of the data after ft_checkdata(varargin{i}, 'datatype', {'source', 'volume'}, 'feedback', 'no', 'inside', 'index', 'sourcerepresentation', 'new'); in the new implementation of ft_sourcestatistics:



varargin{1}

ans =



(before ft_checkdata:)



        pos: [8196x3 double]
        var: [1x1 struct]
     dimord: 'voxel'
      trial: [1x10 struct]
     inside: [8196x1 double]
    outside: [0x1 double]
         df: [8196x1 double]
        cfg: [1x1 struct]



(after ft_checkdata:)



          pos: [8196x3 double]
          var: [1x1 struct]
       dimord: 'pos'
       inside: [8196x1 double]
      outside: [0x1 double]
           df: [8196x1 double]
          cfg: [1x1 struct]
          pow: [8196x10 double]
    powdimord: 'pos'



This leads to a (wrong) transpose of the design (originally row1 = uvar, row2 = ivar [with two conditions for a depsamples T test]) and ultimately to the message

'The data must contain at least two units (usually subjects).'



Any help would be much appreciated, thanks very much!

Max

(fieldtrip version: fieldtrip-lite-20111130 on a Windows7 PC)



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