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From: Rune Allnor on 11 Mar 2010 12:46
On 11 Mar, 18:23, "Hans " <te...(a)gmx.com> wrote:
> Jep, Rune You are completely right, in your suspicion, what the hard part is for me :-)
>
> I have an idea about the "dip" in the signals I want to filter out in my data if we look at them in the non transformed data. So it's a linear relation between f and k or x and y, depending how You call the 2 dimensions.
>
> How can I create a filter from my linear equations in the f-k domain ?

You can't. You fill in the numbers in the matrix (or N-D array, if
you have more than one spatial dimension) H I showed you a couple
of posts back. There is nothing more to it. You just have to know
what numbers to fill in. And they have nothing to do with anything
else than the job you want the filter to do.

Rune
From: Hans on 12 Mar 2010 05:22
Sorry, I think I didn't chose the right words, to not be misunderstood.

Assuming I have a data matrix with Y X (Y=time;X=way) and I have a noise signal with Y/X = 1 contained in it, that I want to filter out.
Is there an easy way to tell, how the apllied (filter) matrix would like ? Or do You have a suggestion, where to look for ?

Thank You
hans
From: Rune Allnor on 12 Mar 2010 05:33
On 12 Mar, 11:22, "Hans " <te...(a)gmx.com> wrote:
> Sorry, I think I didn't chose the right words, to not be misunderstood.
>
> Assuming I have a data matrix with Y X  (Y=time;X=way) and I have a noise signal with Y/X = 1 contained in it, that I want to filter out.
> Is there an easy way to tell, how the apllied (filter) matrix would like ?

No. The basic principle is that any spectrum coefficient
you want gone should be multiplied with a small number,
roughly 0, while the spectrum coefficients you want to
keep should be mutliplied by a large number, around 1.

This is straight-forward idea is severely complicated by
the fact that any modification you do to the fk-domain
filter matrix has effect all over tx domain - be too hard
in one spot in fk domain will mess up everything in tx
domain. Which is why you need to know what you are doing.

Talk with your boss or supervisor for help on where to
find material suitable for your level.

Rune
From: Hans on 12 Mar 2010 06:55
Unfortunately there is no one here around to talk to about this kind of topic. I know that this filter type is widely used in seismic data processing, where relatively easy to use filters exist. So it seems some software is easy to work with. But of cause this special software works only with their special data format.
I hoped something similar would exist in Matlab - from Mathworks or created by a user.

Thank You for the discussion.

Hans
From: Hans on 12 Mar 2010 16:44
I've transformed my matrix into reflection seismic data format and loaded it into processing software.
There is a tool, that performs a f-k transformation and plots a f-k diagram.
In this diagram You can mark an area in the f-K domain by mouse click which should be filtered out.
The result of this filtering is plotted in another window.

I think it should be possible too to generate a tool like this in Matlab .... but of cause it will be some work.
So it was much more comfortable to change data format.

hans
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