[FieldTrip] Wavelet spectrum is cut strangely on low frequencies

[Arjen Stolk]

Hi Diana,

This is because your time points of interest are close to the boundaries of
the original time series, as described here:
http://www.fieldtriptoolbox.org/faq/why_does_my_tfr_contain_nans

You may want to include more data from your original time series (at call
to ft_definetrial / ft_preprocessing) or use smaller spectral windows /
fewer wavelet cycles (at ft_frequencyanalysis, spectral resolution
permitting).

Best regards,
Arjen


On Sun, May 20, 2018 at 8:08 AM, - Диана <diana-hime at yandex.ru> wrote:

> Hello!
>
> My name is Diana. Currently I'm triyng to do a wavelet analysis of my
> data, which is 128 (129 with reference elctrode) EEG recording.
>
> The problem is thatthe result looks strangely - the low frequencies are
> cut off. Can't understand the reason for this, and should it be this way or
> it not.  Would be happy with any help)
>
> The script I use:
>
> %preprocessing
> cfg = [];
> cfg.dataset = FileName;
> cfg.continuous   = 'yes'; %считываем файл как непрерывный
> data_preproc = ft_preprocessing(cfg);
>
>
> % deftrial
>  cfg = [];
>   cfg.dataset                 = FileName;
>   cfg.trialdef.eventtype      = 'trigger';
>   cfg.trialdef.eventvalue     = 'tim0';
>   cfg.trialdef.prestim        = 0.2;
>   cfg.trialdef.poststim       = 2.2;
>
>   cfg_deftrial = ft_definetrial(cfg);
>
> data_deftrialed = ft_redefinetrial(cfg_deftrial, data_preproc);
>
> %wavelet
>
>     cfg = [];
>     cfg.channel    = 'all';
>     cfg.method     = 'wavelet';
>        cfg.width      = 7;
>     cfg.output     = 'pow';
>     cfg.foi        = 1:1:45;
>     cfg.toi        = 1:0.01:2;
>     TFRwave = ft_freqanalysis(cfg, data_deftrialed);
>
>
>
>    The wavelet I get:
>
>
>
>
>
> Thanks in advance, Diana.
> Undergraduate Student
> Department of Biology of MSU
>
> P.S: Sorry for my english this time...
>
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>
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