Daubechies-4 wavelet transform in MATLAB

Started by April 14, 2010
```Hello:

I have a 4x4 matrix which I wish to decompose into 4 frequency bands
(LL, HL, LH, HH where L=low, H=high) by using a one-level Daubechies-4
wavelet transform. As a result of the transform, each band should
contain 2x2 coefficients. How can I do this in MATLAB? I know that
MATLAB has dbaux and dbwavf functions. However, I'm not sure how to
use them and I also don't have the wavelet toolbox.

I have read the wikipedia article (http://en.wikipedia.org/wiki/
Daubechies_wavelet) and also this paper (http://www.springerlink.com/
content/57540u87733k1861/fulltext.pdf). I have no prior experience
necessary so any help is greatly appreciated.

Thanks.
```
```On 14 apr, 23:04, Mariya <mariya.nago...@gmail.com> wrote:
> Hello:
>
> I have a 4x4 matrix which I wish to decompose into 4 frequency bands
> (LL, HL, LH, HH where L=low, H=high) by using a one-level Daubechies-4
> wavelet transform. As a result of the transform, each band should
> contain 2x2 coefficients. How can I do this in MATLAB? I know that
> MATLAB has dbaux and dbwavf functions. However, I'm not sure how to
> use them and I also don't have the wavelet toolbox.

Well, both those functions are from the wavelet toolbox,
so getting that toolbox would be an obvious starting point.
Once you get it, there is a chance that there is some
documentation included, which might help explain how to
use the functions...

Rune
```
```On Apr 14, 5:10&#4294967295;pm, Rune Allnor <all...@tele.ntnu.no> wrote:
> On 14 apr, 23:04, Mariya <mariya.nago...@gmail.com> wrote:
>
> > Hello:
>
> > I have a 4x4 matrix which I wish to decompose into 4 frequency bands
> > (LL, HL, LH, HH where L=low, H=high) by using a one-level Daubechies-4
> > wavelet transform. As a result of the transform, each band should
> > contain 2x2 coefficients. How can I do this in MATLAB? I know that
> > MATLAB has dbaux and dbwavf functions. However, I'm not sure how to
> > use them and I also don't have the wavelet toolbox.
>
> Well, both those functions are from the wavelet toolbox,
> so getting that toolbox would be an obvious starting point.
> Once you get it, there is a chance that there is some
> documentation included, which might help explain how to
> use the functions...
>
> Rune

That is an expensive answer if it is gotten legitimately.

Cheaper solution, web search.

Dirk
```
```On 15 apr, 19:49, Dirk Bell <bellda2...@cox.net> wrote:
> On Apr 14, 5:10&#4294967295;pm, Rune Allnor <all...@tele.ntnu.no> wrote:
>
>
>
>
>
> > On 14 apr, 23:04, Mariya <mariya.nago...@gmail.com> wrote:
>
> > > Hello:
>
> > > I have a 4x4 matrix which I wish to decompose into 4 frequency bands
> > > (LL, HL, LH, HH where L=low, H=high) by using a one-level Daubechies-4
> > > wavelet transform. As a result of the transform, each band should
> > > contain 2x2 coefficients. How can I do this in MATLAB? I know that
> > > MATLAB has dbaux and dbwavf functions. However, I'm not sure how to
> > > use them and I also don't have the wavelet toolbox.
>
> > Well, both those functions are from the wavelet toolbox,
> > so getting that toolbox would be an obvious starting point.
> > Once you get it, there is a chance that there is some
> > documentation included, which might help explain how to
> > use the functions...
>
> > Rune
>
> That is an expensive answer if it is gotten legitimately.

I've heard some rumours that matlab has some safety features
built in, such that a function name from a toolbox you do
not have a lisence for somehow gets blocked. I haven't tested
it - don't even know if it is true - but this seems to be a
'reasonable' countermeasure against pirate versions of useful
functions. (Although it would be a nuisance for somebody who
might want to write a function with a name that happens to be
taken by a toolbox function.)

So if the OP wants to use those functions mentioned, getting
the toolbox seems to be the only option.

> Cheaper solution, web search.

Or learning the material from scratch and implement yourself.
But that was, of course, what you meant...?

Rune
```
```On Apr 15, 2:05&#4294967295;pm, Rune Allnor <all...@tele.ntnu.no> wrote:
> On 15 apr, 19:49, Dirk Bell <bellda2...@cox.net> wrote:
>
>
>
>
>
> > On Apr 14, 5:10&#4294967295;pm, Rune Allnor <all...@tele.ntnu.no> wrote:
>
> > > On 14 apr, 23:04, Mariya <mariya.nago...@gmail.com> wrote:
>
> > > > Hello:
>
> > > > I have a 4x4 matrix which I wish to decompose into 4 frequency bands
> > > > (LL, HL, LH, HH where L=low, H=high) by using a one-level Daubechies-4
> > > > wavelet transform. As a result of the transform, each band should
> > > > contain 2x2 coefficients. How can I do this in MATLAB? I know that
> > > > MATLAB has dbaux and dbwavf functions. However, I'm not sure how to
> > > > use them and I also don't have the wavelet toolbox.
>
> > > Well, both those functions are from the wavelet toolbox,
> > > so getting that toolbox would be an obvious starting point.
> > > Once you get it, there is a chance that there is some
> > > documentation included, which might help explain how to
> > > use the functions...
>
> > > Rune
>
> > That is an expensive answer if it is gotten legitimately.
>
> I've heard some rumours that matlab has some safety features
> built in, such that a function name from a toolbox you do
> not have a lisence for somehow gets blocked. I haven't tested
> it - don't even know if it is true - but this seems to be a
> 'reasonable' countermeasure against pirate versions of useful
> functions. (Although it would be a nuisance for somebody who
> might want to write a function with a name that happens to be
> taken by a toolbox function.)
>
> So if the OP wants to use those functions mentioned, getting
> the toolbox seems to be the only option.
>
> > Cheaper solution, web search.
>
> Or learning the material from scratch and implement yourself.
> But that was, of course, what you meant...?
>
> Rune- Hide quoted text -
>
> - Show quoted text -

That is what I meant (I like to understand what I use, I have little
faith in unknown apps), but I guess realistically it may not be the
most efficient way.

Dirk
```