[FieldTrip] ft_preprocessing filter order

Robert Oostenveld r.oostenveld at donders.ru.nl
Wed Oct 17 12:48:11 CEST 2018


Hi Alessandro

If you would want to apply them in a different order, just call ft_preprocessing multiple times, once for every filter you want to apply.

best
Robert


> On 17 Oct 2018, at 00:54, Alessandro Orticoni <alessandro.orticoni at gmail.com> wrote:
> 
> Hi,
> 
> Yes, thanks both! You have been very helpful.
> 
> Best,
> Alessandro
> 
> Il giorno mer 17 ott 2018 alle ore 00:17 Diego Lozano-Soldevilla <dlozanosoldevilla at gmail.com <mailto:dlozanosoldevilla at gmail.com>> ha scritto:
> Hi Alessandro,
> 
> As explained in the help  <https://github.com/fieldtrip/fieldtrip/blob/master/ft_preprocessing.m#L55>of ft_preprocessing, the default filter order can be found in the low level functions:
> fieldtrip/preproc/ft_preproc_bandpassfilter.m
> fieldtrip/preproc/ft_preproc_bandstopfilter.m
> fieldtrip/preproc/ft_preproc_highpassfilter.m
> fieldtrip/preproc/ft_preproc_lowpassfilter.m
> 
> The filter order means something very different for the Butterworth (i.e. amount of samples used for the input-output recursion) 
> https://github.com/fieldtrip/fieldtrip/blob/master/preproc/ft_preproc_bandpassfilter.m#L151 <https://github.com/fieldtrip/fieldtrip/blob/master/preproc/ft_preproc_bandpassfilter.m#L151>
> 
> or for the Finite Impulse Response (FIR) filter (i.e. length of the filter kernel).
> https://github.com/fieldtrip/fieldtrip/blob/master/preproc/ft_preproc_bandpassfilter.m#L235 <https://github.com/fieldtrip/fieldtrip/blob/master/preproc/ft_preproc_bandpassfilter.m#L235>
> 
> For the ones interested to know more about what that number does for different filters, please check this example script:
> http://www.fieldtriptoolbox.org/example/determine_the_filter_characteristics <http://www.fieldtriptoolbox.org/example/determine_the_filter_characteristics>
> 
> I hope that helps,
> 
> Diego
> 
> 
> On Tue, 16 Oct 2018 at 23:13, Alessandro Orticoni <alessandro.orticoni at gmail.com <mailto: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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