[Eeglablist] applying CleanLine results to unfiltered data

[Raquel London]

Hi Andreas,

Thank you for this advice and helping me understand the mechanics of it all!

Raquel

On Mon, Sep 5, 2016 at 10:54 AM, Andreas Widmann <widmann at uni-leipzig.de>
wrote:

> Hi Raquel,
>
> both high-pass filtering and cleanline are linear operations. You just
> need two subtractions. There are two possible strategies which should end
> up in the identical result.
>
> (1) Subtracting the high-pass filtered and "clean-lined" data from the
> high-pass only data gives you the line noise estimate. You can now subtract
> the line noise estimate from the unfiltered data.
> or
> (2) Subtracting the high-pass filtered data from the unfiltered data gives
> you the low frequency part of the data. You can then add the low frequency
> part back to the high-pass filtered and "clean-lined" data.
>
> Make sure to work with double precision data as recommended in the
> subsequent paragraph of the quoted ref.
>
> Hope this helps! Best,
> Andreas
>
> > Am 01.09.2016 um 20:59 schrieb Raquel London <raquellondon at gmail.com>:
> >
> > Dear eeglab list,
> >
> > I am interested in using CleanLine to get rid of 50 Hz line noise.
> However, as I understand from the information I could find, it is important
> to use a ~1 Hz highpass filter on the data before applying the CleanLine
> algorithm. I would prefer to use the method described in the PREP pipeline:
> http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4471356/
> >
> > "We obtain essentially the same results if we high-pass the original
> signal, remove line noise from the high-passed signal, and capture the
> signal that was removed. We subtract the captured noise signal from the
> original signal to obtain a “cleaned” unfiltered signal. If we subsequently
> high-pass filter the cleaned unfiltered signal, we find the line noise has
> been removed as though the signal had been filtered prior to line noise
> removal. The result is similar for a 1 Hz high-pass filter. The PREP
> pipeline uses this strategy for its line noise removal to avoid committing
> to a filtering strategy for the final pipeline output."
> >
> > However, and I apologize if this is a stupid question.., I am not able
> to figure out how to implement this strategy. Is there any variable or set
> of variables I can save after running CleanLine that I can then apply to
> the unfiltered data, similar to what you can do with ICA weights?
> >
> > Thank you!
> >
> > Raquel
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