[Eeglablist] causal filtering pop_eegfiltnew

[Andreas Widmann]

> actually from what I see in eegfilt.m, if causal option is on, it uses filter.m (phase shift introduced), otherwise is causal option is off it uses filtfilt.m (no phase shift).
> 
> so, if you don't want the phase shift, you should NOT check the "use causal filter" box.
> 
> do you confirm this, or is there a confusion with the nomenclature?
Yes, this is correct. However, if you want a zero-phase/non-causal filter you should use the *new* basic FIR filter, which also provides zero-phase filtering.

Best,
Andreas

> 
> d.
> 
> 
> On Wed, Apr 24, 2013 at 10:10 PM, Makoto Miyakoshi <mmiyakoshi at ucsd.edu> wrote:
>> Dear Marta,
>> 
>> > if i want to get a causal filter i should be using the 'legacy' version of the pop_eegfilt that uses fir1 and firfirl to filter the data? 
>> 
>> Right. Check the box 'use causal filter' when you run it.
>> 
>> Makoto 
>> 
>> 
>> 2013/4/24 Marta Castellano <m at martacastellano.eu>
>>> Dear eeglablist,
>>> 
>>> I would need some help regarding the filtering of EEG data. 
>>> 
>>> I'm currently using the EEGlab 12.0.2.0b and filtering the data with pop_eegfiltnew, which creates a type 1 windowed synch filter and the filtering is implemented through firfirlt. As far as I understood, this leads to a phase shift because of the firfilt, and also, given that the impulse response of the filter is symetric, the filter is acausal (so that no causal analysis can be performed). 
>>> 
>>> Does that means that, if i want to get a causal filter i should be using the 'legacy' version of the pop_eegfilt that uses fir1 and firfirl to filter the data? 
>>> 
>>> Thanks a lot in advance for your help,
>>> 
>>> Marta
>>> 
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>> 
>> 
>> 
>> -- 
>> Makoto Miyakoshi
>> Swartz Center for Computational Neuroscience
>> Institute for Neural Computation, University of California San Diego
>> 
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