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Re: Discrete wavelet analysis


From: Helios de Rosario
Subject: Re: Discrete wavelet analysis
Date: Mon, 30 Jun 2014 14:35:35 +0200

Helios De Rosario wrote:

>>
>> I'm interested in multiresolution analysis with wavelets in Octave.
My
>> starting point is some routines that use functions from Matlab's
Wavelet
>> Toolbox, so things would be easier if there were some package for
Octave
>> that defines them.
>>
>> However, I'm not sure what is the current situation in relation to
this
>> topic. I have read recommendations to using WaveLab, or the package
>> ltfat, that implement a wide array of functions to work with
wavelets.
>> That might be ok for my purposes, although the transition from
Matlab
>> would not be that straightforward.
>>
[...]

Peter Søndergaard wrote:

> I am the original author of LTFAT, so my view is perhaps a little
biased,
> but here goes:
> 
> We have intentionally not chosen to make a functionally equivalent
version
> of the Matlab Wavelet package, mainly because we never considered it
to be
> very good.  The output of the functions depends strongly on a global
> variable, which is not a very portable behaviour.
> 
> In LTFAT there are very good implementations of the discrete wavelet
> transform:
> 
> http://ltfat.sourceforge.net/doc/wavelets/fwt.php 
> http://ltfat.sourceforge.net/doc/wavelets/ifwt.php 
> 
> and a bunch of different filters to choose from, see the "Filters
defined
> in the time‑domain" headline here:
> 
> http://ltfat.sourceforge.net/doc/wavelets/index.php 
> 
> Wavelab is also a good package, it has just not been updated for
many
> years, and as I recall you need to do some simple modification to get
it
> working in Octave. LTFAT works out of the box.
> 

Thanks, Peter. Octave's wiki only pointed to Wavelab. I have also added
a link to LTFAT, accordingly:
http://wiki.octave.org/Code#Various_Communications-Related_Octave_Code

I still think that Matlab-like functions are valuable, to allow re-use
Matlab code. Perhaps they could be (partially) wrappers to LTFAT's
package? The only drawback is that this would add yet another dependency
in package "signal", I don't know what the maintainers of signal might
think of it.

Best regards,
Helios


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