Discover MakerZone

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn more

Discover what MATLAB® can do for your career.

Opportunities for recent engineering grads.

Apply Today

Thread Subject:
Denoising using wavelets

Subject: Denoising using wavelets

From: Filipe Magalhães

Date: 29 Oct, 2005 09:29:24

Message: 1 of 2

Hello all!

I'm here with a series of problems/questions with wavelets denoising
tools...

First of all I'd like to know if in the function ddencmp the returned
default values vary from signal to signal?
I've already checked that the threshold value that is returned
varies from signal to signal, but the others 'SORH' and KEEPAPP,
always return 's' and 1, respectively, what does that mean? Does
"MATLAB" thinks that SORH='s' and KEEPAPP=1 is better for all the
cases or was just mere coincidence in all the signals I analised?

In the help page for the wdencmp function it says "If KEEPAPP = 1,
approximation coefficients cannot be thresholded, otherwise it is
possible." - what does this means?
And it also refers global threshold values or level-dependent
threshold values, but if I use the ddencmp function the threshold
returned variable always returns a single value, how can I use it to
level-dependent thresholding in the wdencmp function, seeing that in
the help page of that function it says "THR must be of
length N)" - for level-dependent thresholding...

Other thing is that no matters which level "N" I use in the wden
function it always returns me the same XD
[XD,CXD,LXD] = WDEN(X,TPTR,SORH,SCAL,N,'wname')
why does that happen?

And at last, which function do you advise me to use to denoise a
signal? wden or wdencmp? ;)

Thanks in advance and sorry for this long post!

Filipe Magalhães

Subject: Denoising using wavelets

From: NEBRAS SOBAHI

Date: 26 Jun, 2013 22:57:08

Message: 2 of 2

Hello,

Have you received any reply or an answer for your questions. I really need to find answering for your question because I am working on the same thing. Could you reply me if you know the answer.


"Filipe Magalhães" <filipe.tiago@REMOVETHIS.sapo.pt> wrote in message <ef19c99.-1@webx.raydaftYaTP>...
> Hello all!
>
> I'm here with a series of problems/questions with wavelets denoising
> tools...
>
> First of all I'd like to know if in the function ddencmp the returned
> default values vary from signal to signal?
> I've already checked that the threshold value that is returned
> varies from signal to signal, but the others 'SORH' and KEEPAPP,
> always return 's' and 1, respectively, what does that mean? Does
> "MATLAB" thinks that SORH='s' and KEEPAPP=1 is better for all the
> cases or was just mere coincidence in all the signals I analised?
>
> In the help page for the wdencmp function it says "If KEEPAPP = 1,
> approximation coefficients cannot be thresholded, otherwise it is
> possible." - what does this means?
> And it also refers global threshold values or level-dependent
> threshold values, but if I use the ddencmp function the threshold
> returned variable always returns a single value, how can I use it to
> level-dependent thresholding in the wdencmp function, seeing that in
> the help page of that function it says "THR must be of
> length N)" - for level-dependent thresholding...
>
> Other thing is that no matters which level "N" I use in the wden
> function it always returns me the same XD
> [XD,CXD,LXD] = WDEN(X,TPTR,SORH,SCAL,N,'wname')
> why does that happen?
>
> And at last, which function do you advise me to use to denoise a
> signal? wden or wdencmp? ;)
>
> Thanks in advance and sorry for this long post!
>
> Filipe Magalhães

Tags for this Thread

No tags are associated with this thread.

What are tags?

A tag is like a keyword or category label associated with each thread. Tags make it easier for you to find threads of interest.

Anyone can tag a thread. Tags are public and visible to everyone.

Contact us