[Mne_analysis] Badly resample signal
Phillip Alday
phillip.alday at mpi.nl
Thu Aug 22 05:02:36 EDT 2019
External Email - Use Caution
If you don't care about signals above > 100 Hz, then you by definition
don't care about high frequency stuff.
You have to choose.
That said, there is a lot of documentation on the MNE website about
resampling:
http://martinos.org/mne/stable/auto_examples/preprocessing/plot_resample.html#sphx-glr-auto-examples-preprocessing-plot-resample-py
http://martinos.org/mne/stable/search.html?q=resampling&check_keywords=yes&area=default
On 22/08/2019 11:59, RODNEY PETRUS BALANDONG wrote:
>
> I only interested with the signal up to 100Hz, so it redundant and
> computationally expensive to handle signal with 1000Hz.
>
>
>
> I'm just curious whether ignoring those brief high-frequency peaks
> will affect the overall analysis later. So, if there is a way to
> these brief high-frequency would be an advantage.
>
>
>
> Anyhow, is it common practice to neglect the brief high-frequency peaks?
>
>
>
> *From:*Phillip Alday <phillip.alday at mpi.nl>
> *Sent:* Thursday, 22 August, 2019 4:53 PM
> *To:* RODNEY PETRUS BALANDONG <rodney.petrus_g03291 at utp.edu.my>
> *Cc:* mne_analysis at nmr.mgh.harvard.edu
> *Subject:* Re: [Mne_analysis] Badly resample signal
>
>
>
> But why do you need to resample? That's what I meant with an XY problem.
>
> Why do you care about brief high-frequency peaks?
>
> Phillip
>
> On 22/08/2019 11:46, RODNEY PETRUS BALANDONG wrote:
>
> I need to downsample an original signal that sampled at 1000Hz to
> 100Hz.
>
>
>
> *From:*Phillip Alday <phillip.alday at mpi.nl>
> <mailto:phillip.alday at mpi.nl>
> *Sent:* Thursday, 22 August, 2019 4:44 PM
> *To:* RODNEY PETRUS BALANDONG <rodney.petrus_g03291 at utp.edu.my>
> <mailto:rodney.petrus_g03291 at utp.edu.my>
> *Cc:* mne_analysis at nmr.mgh.harvard.edu
> <mailto:mne_analysis at nmr.mgh.harvard.edu>
> *Subject:* Re: [Mne_analysis] Badly resample signal
>
>
>
> Appropriate filtering may help with some things, but .... I think
> we're heading into XY question territory here
> (http://xyproblem.info/).
>
> Why do you want to resample? What are you trying to accomplish?
>
> Phillip
>
> On 22/08/2019 11:38, RODNEY PETRUS BALANDONG wrote:
>
> Dear Phillip,
>
>
>
> Thanks for the response,
>
>
>
> Just wonder whether there exist different technique to address
> such an issue? For example, rather than using the averaging
> approach
>
>
>
> Regards
>
> Rodney
>
>
>
> *From:*Phillip Alday <phillip.alday at mpi.nl>
> <mailto:phillip.alday at mpi.nl>
> *Sent:* Thursday, 22 August, 2019 4:33 PM
> *To:* Discussion and support forum for the users of MNE
> Software <mne_analysis at nmr.mgh.harvard.edu>
> <mailto:mne_analysis at nmr.mgh.harvard.edu>; RODNEY PETRUS
> BALANDONG <rodney.petrus_g03291 at utp.edu.my>
> <mailto:rodney.petrus_g03291 at utp.edu.my>
> *Subject:* Re: [Mne_analysis] Badly resample signal
>
>
>
> This is expected behavior for resampling. With resampling, you
> lose temporal resolution, so fast, high amplitude deviations
> are lost. This is what happens at the beginning of your
> signal. Later in the signal you see that the slower change in
> the mean of the signal is preserved, but the bumps are list.
>
> Intuitively: you have fewer samples, so you can't capture both
> the deviations up and the deviations down, so they average out
> and you get just the mean. So the big peak and big trough
> early in your example just cancel out when resampled.
>
> Phillip
>
> On 22/08/2019 07:01, RODNEY PETRUS BALANDONG wrote:
>
> * External Email - Use Caution *
>
> Dear All,
>
>
>
> The issue is about sample badly approximated
>
>
>
> Given an original signal sampled at 100Hz, the objective
> was to downsampled it into 50 Hz
>
> The downsampling process was realised using the MNE resample.
>
>
>
> However, as can be noticed from the image below, the
> sample is badly approximated. Instead of registering the
> original signal magnitude, the function RESAMPLE return an
> approximated signal magnitude.
>
>
>
> This rise two question
>
> 1. Is it common for such badly resample to occur?
> 2. If yes, how to minimize this
>
>
>
> The problem can be reproduced using the notebook which is
> accessible through this link
> <https://github.com/balandongiv/EyeCloseOpen/blob/master/HelpImportDownsample_EDF.ipynb>.
>
>
>
> Thanks in advance for entertaining this request
>
>
>
>
>
> A close up of a map Description automatically generated
>
>
>
>
>
> Regards
>
> Rodney
>
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> Universiti Teknologi PETRONAS (UTP).
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> DISCLAIMER : This e-mail and any files transmitted with it ("Message")
> is intended only for the use of the recipient(s) named above and may
> contain confidential information. You are hereby notified that the
> taking of any action in reliance upon, or any review, retransmission,
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