[FieldTrip] [Fieldtrip] Line noise Removal

[Alessandro Orticoni]

Dear experts,

I'm basically a beginner in coding with Fieldtrip, and I'm having a problem
with line noise filtering.
I would like to remove it from the heart rate signal, and I tried just
typing 'yes' at the option cfg.dftfilter.
But is doesn't seem to work, since the power spectrum contains the 50Hz and
her harmonics even after the filtering.

You can find the code in the following lines:

%% ===FREQUENCY Pre Filtering VERIFICATION===
fs=data.fsample;

cfg = [];
cfg.output        = 'pow';
cfg.channel       = 'ECG 2';
cfg.method        = 'mtmfft';
cfg.taper         = 'hanning';
cfg.pad           = 'nextpow2';
cfg.foilim        = [0.3 fs/2]; % teorema di Nyquist
freq_epoched_Cz   = ft_freqanalysis(cfg, data_epoched_Cz);

%% ===Plot Spectra===
figure;
plot(freq_epoched_Cz.freq,mag2db(freq_epoched_Cz.powspctrm));

%% ===Filtering===
cfg            = [];
cfg.channel    = {'ECG 2'};
cfg.dftfilter  = 'yes';
ECG_Filtered   = ft_preprocessing(cfg,data_Cz);

cfg          = [];
cfg.length   = 30; % in seconds;
cfg.overlap  = 0;
data_epoched_ECG_Filtered = ft_redefinetrial(cfg, ECG_Filtered);

cfg = [];
cfg.output        = 'pow';
cfg.method        = 'mtmfft';
cfg.taper         = 'hanning';
cfg.pad           = 'nextpow2';
cfg.foilim        = [0.3 fs/2]; % teorema di Nyquist
freq_epoched_Cz_Filtered = ft_freqanalysis(cfg, data_epoched_ECG_Filtered);

%% ===Plot Spectra===
plot(freq_epoched_Cz_Filtered.freq,mag2db(freq_epoched_Cz_Filtered.powspctrm));

Thanks a lot.

Kind regards,
Alessandro Orticoni
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