[FieldTrip] filtering during artifact detection

[Diego Lozano-Soldevilla]

Dear Maximilien,

You should specify the filter parameters in the cfg:

    cfg.artfctdef.eog.bpfilter   = 'yes'
   cfg.artfctdef.eog.bpfilttype = 'but';% or any other filter type you
want to use, see help ft_preprocessing for more details
    cfg.artfctdef.eog.bpfreq     = [1 15]
    cfg.artfctdef.eog.bpfiltord  = 4; % goes hand-by-hand with the
filter type; see


Take a look to the fft_artifact_eog.m documentation. To know more about
filtering you might want to take a look here:
http://www.fieldtriptoolbox.org/example/determine_the_filter_characteristics

Best,

Diego

On 26 October 2016 at 10:42, Maximilien Chaumon <
maximilien.chaumon at gmail.com> wrote:

> Dear all,
> when attempting to detect blinks automatically on a continuous recording
> without EOGs, I use a few frontal sensors and ft_artifact_eog as follows:
>
>         cfg                         = [];
>         cfg.dataset                 = fullfile(rootdir,f{iD});
>         cfg.layout                  = 'neuromag306mag.lay';
>         cfg.trialdef.eventtype      = 'STI101';
>         cfg.trialdef.eventvalue      = {255};
>         cfg                          = ft_definetrial(cfg);
>
>         cfg.trl                     = [cfg.trl(1,1) cfg.trl(end,2) 0];
>         cfg.channel                 = 'megmag';
>         cfg.continuous              = 'yes';
>         data                        = ft_preprocessing(cfg);
>
>
>         cfg.artfctdef.eog           = [];
>         cfg.artfctdef.eog.channel   = eogchans;
>         cfg.artfctdef.eog.trlpadding = 0;
>         cfg.artfctdef.eog.interactive = 'yes';
>
>         [cfg, artifact{iC,iD}]      = ft_artifact_eog(cfg,data);
>
> This opens an interactive window in which the EOG signal is not
> BPfiltered, and contains in particular slow drifts that make the threshold
> detection pretty inefficient. I'm surprised because cfg.artfctdef is
> supposed to bpfilter 1-15Hz the data, isn't it?
>
> Is this normal?
> Thanks,
> Max
>
>
>
>
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