[FieldTrip] FFT on a single concatenate trial

[Eelke Spaak]

Dear Elisa,

Raw data is represented with time axes and trials in a cell array (one
element per trial), so if you do

appended.trial = {appended.trial};
appended.time = {appended.time};

it should work.

Best,
Eelke

On 4 February 2014 10:36, elisa filevich <elisa.filevich at gmail.com> wrote:
> Dear all,
>
> I'm doing frequency tagging on relatively short epochs. My frequency
> components are clearly there, but the signal-to-noise ratio is very low. In
> order to improve SNR, I want to try to concatenate the individual trials
> (with the appropriate epoch length to keep the frequency constant).
>
> I simply concatenated all trial and timepoints vectors into a single trial
> structure, and I now have may data in a structure that has the following
> fields:
>
>
> appended =
>
>       label: {1x22 cell}
>     fsample: 512
>        elec: [1x1 struct]
>       trial: [22x157990 single]
>        time: [1x157990 double]
>
>
> I then run the FFT below, and I get the following error:
>
>    error('the data does not contain a dimord, but it also does not resemble
> raw or component data');
>
> Is it possible to run FFT on a single trial? Is there a way to work around
> this?
>
> Best
> Elisa
>
>
> cfg              = [];
> cfg.output       = 'pow';
> cfg.channel      = 'all';
> cfg.method       = 'mtmfft';
> cfg.taper        = 'hanning';
> cfg.foi          = 5:.5:35;
> cfg.keeptrials   = 'no';
> FFThann          = ft_freqanalysis(cfg, epoched);
>
>
>
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