[FieldTrip] help with output structure of 'ft_sourceanalysis'

[Sajeev Kunjan]

Dear Fieldtrip,

As part of my research I am using fieldtrip to do connectivity analysis.
But I am really struggling to get my code working.If someone is able to
help me with the question below it would be a great help.

Basically what I want to understand, what each field of the output of
'ft_sourceanalysis' means, especially 'trial.filter'.


My intermediate output structure and configurations are shown below. It is
a 108 channel 50001 sample EEG time series.




data
-----

    sampleinfo: [1 50001]
       fsample: 5000
          elec: [1×1 struct]
           hdr: [1×1 struct]
         trial: {[108×50001 double]}
          time: {[1×50001 double]}
         label: {108×1 cell}
           cfg: [1×1 struct]


timelock
--------
cfg = [];
cfg.channel = 'EEG';
cfg.vartrllength = 2;
cfg.covariance = 'yes';
cfg.covariancewindow = 'all';
cfg.keeptrials = 'yes';

timelock = ft_timelockanalysis(cfg, data);

timelock =
  struct with fields:

      time: [1×50001 double]
     label: {108×1 cell}
      elec: [1×1 struct]
     trial: [1×108×50001 double]
    dimord: 'rpt_chan_time'
       cov: [1×108×108 double]
       cfg: [1×1 struct]



leadfield
---------
grid = ft_prepare_leadfield( cfg, timelock);

grid =
  struct with fields:

                pos: [6804×3 double]
               unit: 'mm'
                dim: [18 21 18]
             inside: [6804×1 logical]
                cfg: [1×1 struct]
          leadfield: {1×6804 cell}
              label: {108×1 cell}
    leadfielddimord: '{pos}_chan_ori'


source analysis
-----------------
cfg = [];
cfg.channel = 'EEG';
cfg.method = 'lcmv';
cfg.sourcemodel = grid;
cfg.headmodel = vol;
cfg.rawtrial = 'yes';
cfg.lcmv.keepfilter = 'yes';
cfg.keepleadfield = 'yes';
cfg.lcmv.projectnoise = 'yes';
cfg.lcmv.lambda = '2%';
source = ft_sourceanalysis( cfg, timelock);

source =
  struct with fields:

               time: [1×50001 double]
                cfg: [1×1 struct]
                dim: [18 21 18]
             inside: [6804×1 logical]
              label: {108×1 cell}
          leadfield: {1×6804 cell}
    leadfielddimord: '{pos}_chan_ori'
                pos: [6804×3 double]
             method: 'rawtrial'
              trial: [1×1 struct]
                 df: 1


I am trying to understand the content of source.trial(1).filter, which is a
cell array of size{6804×1 cell}, each cell has metrics of size 3x108.


Thanks for your help in Advance.

Sajeev Kunjan
PhD Scholar, Flinders university
Adelaide, South Australia
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