[Mne_analysis] Badly resample signal

Thu Aug 22 04:59:02 EDT 2019

        External Email - Use Caution        

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
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, dissemination, distribution, printing or copying of this Message or any part thereof by anyone other than the intended recipient(s) is strictly prohibited. If you have received this Message in error, you should delete this Message immediately and advise the sender by return e-mail. Opinions, conclusions and other information in this Message that do not relate to the official business of Universiti Teknologi PETRONAS (UTP) shall be understood as neither given nor endorsed by Universiti Teknologi PETRONAS (UTP).

_______________________________________________

Mne_analysis mailing list

Mne_analysis at nmr.mgh.harvard.edu<mailto:Mne_analysis at nmr.mgh.harvard.edu>

https://mail.nmr.mgh.harvard.edu/mailman/listinfo/mne_analysis
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, dissemination, distribution, printing or copying of this Message or any part thereof by anyone other than the intended recipient(s) is strictly prohibited. If you have received this Message in error, you should delete this Message immediately and advise the sender by return e-mail. Opinions, conclusions and other information in this Message that do not relate to the official business of Universiti Teknologi PETRONAS (UTP) shall be understood as neither given nor endorsed by Universiti Teknologi PETRONAS (UTP).
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, dissemination, distribution, printing or copying of this Message or any part thereof by anyone other than the intended recipient(s) is strictly prohibited. If you have received this Message in error, you should delete this Message immediately and advise the sender by return e-mail. Opinions, conclusions and other information in this Message that do not relate to the official business of Universiti Teknologi PETRONAS (UTP) shall be understood as neither given nor endorsed by Universiti Teknologi PETRONAS (UTP).
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, dissemination, distribution, printing or copying of this Message or any part thereof by anyone other than the intended recipient(s) is strictly prohibited. If you have received this Message in error, you should delete this Message immediately and advise the sender by return e-mail. Opinions, conclusions and other information in this Message that do not relate to the official business of Universiti Teknologi PETRONAS (UTP) shall be understood as neither given nor endorsed by Universiti Teknologi PETRONAS (UTP).
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20190822/4941cb10/attachment-0001.html 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.png
Type: image/png
Size: 23070 bytes
Desc: image001.png
Url : http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20190822/4941cb10/attachment-0001.png 