[FieldTrip] how does the time-window work

[Schoffelen, J.M. (Jan Mathijs)]

Hi Ivo,

Please have a look at this FAQ: https://www.fieldtriptoolbox.org/faq/why_does_my_tfr_contain_nans/

If your data segments are relatively short, asking for 7 cycles in the wavelet, might be too much. If your data segments are shorter than the length of the time window, no result will be computed.

Solution: use longer data segments for your analysis.

Best wishes,

Jan-Mathijs

> On 14 Jul 2022, at 14:11, Ivaylo Iotchev via fieldtrip <fieldtrip at science.ru.nl> wrote:
> 
> Dear all,
> 
> I am fairly new to the program fieldtrip and so far rather had used the classical "spectrogram" function for most of my time-frequency analyses. As I am now moving on to this advanced offer I am running up a curious difficulty, which might be in fact just a misunderstanding of how the program "speaks".
> 
> In short, I seem to get results for lower frequencies (< 4 Hz) only with smaller time-windows, which is very counter-intuitive, but possibly this has to do with my reading of the lines.
> 
> So far I assume that for 
> cfg.t_ftimwin (defining the time-window) the following line
> 
> 7./cfg.foi, thus 7 cycles/time-window is the larger time-window compared to
> 1./cfg.foi, i.e. 1 cycle/time-window
> 
> Am I misunderstanding what is meant here by "cycle/window"? Or is this a mistake of specifying some properties of the data and/or method?
> 
> Kind regards! And many thanks for your time if you have any :)
> 
> Dr. Ivaylo (Ivo) Iotchev
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