[FieldTrip] Keeptrials using "pcc" for source analysis

[Xie Wanze]

 Hi Jens,
 Thank you for your response. I figured out where the problem resided.  It
seems to me that the 'PCC' temporarily does not work with the option
"rawtrial = 'yes'".  So, the output from using "keeptrials = 'yes'" does
not contain the pow and mom information for individual trials.  However,
this information can be reconstructed for each trial using the
ft_sourcedescriptive function with "keeptrials = 'yes' ".
 For source analysis of time series (e.g., lcmv and eloreta), individual
trial information can be obtained by setting "keeptrials = 'yes' and
rawtrial = 'yes' ". No need for the ft_sourcedescriptive function.
 I don't know if this was only my case or someone else also had come across
the same situation.



2017-01-04 10:47 GMT-05:00 "Jens Klinzing, Universität Tübingen" <
jens.klinzing at uni-tuebingen.de>:

> Hi Xie,
> are you sure your output does not contain trial data?
>
> If you look in source.avg.mom you should see a cell array containing for
> each inside source point another cell array with as many entries as there
> are trials (I know it is confusing because you expect .avg to contain
> averages, but it may not). The field .csd (cross-spectral density) should
> contain only one (complex-valued) entry per source point since it is
> averaged across trials (or calculated on the average over all trials, not
> sure right now).
>
> By the way: In case you get errors in downstream functions with your
> current output (e.g. when using ft_sourcegrandaverage) check the bugzilla
> on PCC output containing the spatial filter (e.g. http://bugzilla.
> fieldtriptoolbox.org/show_bug.cgi?id=2861 or 3184).
> If you don't really need the filter you can use cfg.keepfilter = 'no' on
> ft_sourceanalysis or remove the filter and filterdimord fields when calling
> functions that would otherwise fail.
>
> Best,
> Jens
>
> Xie Wanze <xiew1202 at gmail.com>
> Samstag, 31. Dezember 2016 15:09
> Dear Fieldtrip community,
> I have a question about using the "keeptrials" option when do the source
> analysis with the beamformer ('PCC') method.   The issue I met was that the
> cfg.keeptrials = 'yes' did not work, i.e., the calculation was not done for
> all the trials but generated averaged output.
>  Has anyone met this issue before? And does anyone know how to fix it?
>  It did not work for my data nor for the data I downloaded from the FT
> database. I attached the codes that I copied from the FT website using the
> FT's example data.
>  I would like to keep the trials information in the source analysis
> because I plan to do the source space connectivity analysis later, which
> needs the individual trials information. Or maybe the "crsspctrm" matrix.
>
> Codes:
>
>  cfg                   = [];
>
> cfg.frequency         = freq.freq;
>
> cfg.method            = 'pcc';
>
> cfg.grid              = lf;
>
> cfg.headmodel         = hdm;
>
> cfg.keeptrials        = 'yes';
>
> cfg.pcc.lambda        = '10%';
>
> cfg.pcc.projectnoise  = 'yes';
>
> cfg.pcc.keepfilter    = 'yes';
>
> cfg.pcc.fixedori      = 'yes';
>
> source = ft_sourceanalysis(cfg, freq);
>
>
> Output ("source"):
>
>     freq: 10
>
>     cumtapcnt: [268x1 double]
>
>           tri: [16000x3 double]
>
>        inside: [8004x1 logical]
>
>           pos: [8004x3 double]
>
>        method: 'average'
>
>           avg: [1x1 struct]
>
>           cfg: [1x1 struct]
>
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