[FieldTrip] ft_preproc_hilbert questions
rmontefusco at med.uchile.cl
Tue Oct 28 21:50:36 CET 2014
To where I understand, yes. Just remember that is amplitude and not power
(you probably knew that). I should remark that the filter part is tricky
On Tue, Oct 28, 2014 at 3:48 PM, Max Cantor <mcantor at umich.edu> wrote:
> Ah, so if I do a narrow BP filter around a single frequency, looped over
> however many frequencies I want, and then restructure the looped data into
> a dimensionally similar matrix as powspctrm in a fieldtrip-type structure,
> I could effectively turn it into a TFR?
> On Tue, Oct 28, 2014 at 3:05 PM, Rodrigo Montefusco <
> rmontefusco at med.uchile.cl> wrote:
>> Hi Max,
>> to what I understand, the output of Hilbert will be the amplitude of the
>> input signal (envelope). If you want to use that information, then the only
>> step you should add before is a very good and sweet narrow band filter (as
>> narrow as you want your frequency bins). Then, the filter design is the
>> hard part, because you need a filter that is able to filter out other
>> frequencies without introducing any kind of artifact.
>> Hopefully someone else has something to add, or if I'm missing any stuff.
>> On Tue, Oct 28, 2014 at 2:16 PM, Max Cantor <mcantor at umich.edu> wrote:
>>> So this is not a specific method-based question, but something more
>>> I've been slowly reading through bits and pieces of Mike Cohen's
>>> 'Analyzing Neural Time Series Data' book, in an attempt to gain a better
>>> understanding of how things like Fourier Transform, Wavelets, and Hilbert
>>> work on a more fundamental level.
>>> Fieldtrip does not have a built in Hilbert time frequency analysis (that
>>> I'm aware of), but from having read through that chapter of Cohen's book
>>> I've been able to effectively create a hilbert analysis of my own.
>>> However, I was wondering if it would be possible to use
>>> ft_preproc_hilbert (setting cfg.hilbert = 'complex', 'real', etc. in
>>> ft_preprocessing) to do this in a more efficient and fieldtrip-compatible
>>> way. It seems I can use this setting to get the analytic signal, phase,
>>> power, and other things, but since this is on raw/epoched data, there is no
>>> obvious way I can think of to apply a time or frequency series as in the
>>> other TFRs. It seems I could either write a fieldtrip function from
>>> scratch, which I'm not prepared to do, or write a function to reformat
>>> fieldtrip data to work using the Cohen function, and then output it back
>>> into a fieldtrip function, which would be fine but I'm more interested to
>>> know if the ft_preproc_hilbert function can do what I want more efficiently.
>>> *So boiling it down**, my questions are:*
>>> 1. Can cfg.hilbert parameter for ft_preprocessing (or ft_preproc_hilbert
>>> called directly) be used as an ad hoc hilbert TFR, and if so what ad hoc
>>> steps would one need to take?
>>> 2. If it cannot be used this way, what situations is it meant for?
>>> Max Cantor
>>> Lab Manager
>>> Computational Neurolinguistics Lab
>>> University of Michigan
>>> fieldtrip mailing list
>>> fieldtrip at donders.ru.nl
>> fieldtrip mailing list
>> fieldtrip at donders.ru.nl
> Max Cantor
> Lab Manager
> Computational Neurolinguistics Lab
> University of Michigan
> fieldtrip mailing list
> fieldtrip at donders.ru.nl
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