[FieldTrip] problem with combing high_pass filter and log transform

[Eelke Spaak]

Hi John,

You're specifying your cfg.hpfreq as a string ('1'), but it should be a
number, so simply 1 without quotes.

Cheers, Eelke

On Thu, 25 Apr 2019, 23:38 John Begnoche, <jbegnoche at sralab.org> wrote:

> Hi Eelke,
>
>
> Thank you for helping. I am applying the High-Pass filter during my
> initial pre-processing (6 min resting state EEG data), here is my code for
> that:
>
> cfg = [];
> cfg.dataset = file;
> cfg.padding = 0;
> cfg.channel = 'all'
> cfg.padtype = 'data';
> cfg.continuous   = 'yes'
>  cfg.hpfilter = 'yes'
>  cfg.hpfreq = '1'
> cfg.trialdef.triallength = 1
> cfg = ft_definetrial(cfg);
> data_segmented_preproc= ft_preprocessing(cfg);
>
>
>
> here is code for my plotting:
>
> %%% PLOT TEST%%%%
>
> cfg = [];
> cfg.channel   = 'eeg 014'
> ft_singleplotER(cfg,freqfourier)
>
>
> Figs are attached.
>
>
> Thanks again,
>
> Patrick
> ------------------------------
> *From:* fieldtrip <fieldtrip-bounces at science.ru.nl> on behalf of Eelke
> Spaak <e.spaak at donders.ru.nl>
> *Sent:* Thursday, April 25, 2019 2:27:24 AM
> *To:* FieldTrip discussion list
> *Subject:* Re: [FieldTrip] problem with combing high_pass filter and log
> transform
>
> Hi Patrick,
>
> Could you provide some more details? First, how are you applying the
> high-pass filter? Also, could you give the code you use for plotting
> and post the resulting figures?
>
> Best,
> Eelke
>
> On Sat, 20 Apr 2019 at 04:53, John Begnoche <jbegnoche at sralab.org> wrote:
> >
> > Hello,
> >
> >
> > I am plotting outcomes from a frequency analysis of resting state sensor
> space EEG data, for the analysis I use the code below, and then plot with
> singleplotER, if I first high pass filter my data at 1Hz during a
> prepocessing step, my plotting shows no activity until 35Hz then it spikes
> to a plateau for the rest of he higher frequencies, after a log transform I
> get a sine wave like shape. With no HP filter the data look like normal
> power spectrum data, why is the HP filter changing my data in this way?
> >
> >
> >     cfg = [];
> >     cfg.output = 'pow' ;
> >     cfg.method = 'mtmfft';
> >     cfg.pad = 'nextpow2';
> >     cfg.taper  = 'hanning';
> >     cfg.foilim = [3 50]; %change for appropriate range of frequencies
> > %     cfg.tapsmofrq = [2] ;
> >     cfg.keeptrials = 'no';
> >     %EEG_freq_segmented{i_run} = ft_freqanalysis(cfg,
> data_segmented_no_artifacts);
> >     %EEG_freq_segmented{i_run} = ft_freqanalysis(cfg, data_segmented);
> >   % freqfourier{i_run} = ft_freqanalysis(cfg,
> data_segmented_preproc_ICArm_no_artifacts);
> >     freqfourier= ft_freqanalysis(cfg, data_segmented_no_artifacts);
> >      %%%%%%log transform%%%%%%%%%%%%%
> >     cfg           = [];
> >     cfg.parameter = 'powspctrm';
> >     cfg.operation = 'log10';
> >     freqfourier    = ft_math(cfg, freqfourier);
> >
> > Thank you,
> > Patrick
> >
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