[FieldTrip] ft_preprocessing filter order

Eugenio Abela abela.eugenio at gmail.com
Tue Oct 16 23:57:12 CEST 2018

Hi Alessandro, 

any defaults are set in the low-level functions that ft_preprocessing calls. So, for the lowpass filter, go have a look at the help of ft_preproc_lowpassfilter.m, it says:

% FT_PREPROC_LOWPASSFILTER applies a low-pass filter to the data and thereby
% removes all high frequency components in the data
% Use as
%   [filt] = ft_preproc_lowpassfilter(dat, Fsample, Flp, N, type, dir, instabilityfix)
% where
%   dat        data matrix (Nchans X Ntime)
%   Fsample    sampling frequency in Hz
%   Flp        filter frequency
%   N          optional filter order, default is 6 (but) or dependent upon
%              frequency band and data length (fir/firls)

The default for the Butterworth low-pass filter is thus 6 (for the bandpass it’s 4). You can set your preferred order when calling ft_preprocessing.m e.g. via cfg.lpfiltord = 4 or whatever makes sense.

Hope that helps


On 16 Oct 2018, at 21:56, Alessandro Orticoni <alessandro.orticoni at gmail.com> wrote:

Dear all,

I would like to ask you just a question: which is the default order of the filters implemented by ft_preprocessing? I cannot find it anywhere.

Thanks a lot,
Alessandro Orticoni 
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