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Re: Re: Multiple application of LinearFilter

• To: mathgroup at smc.vnet.net
• Subject: [mg64901] Re: [mg64856] Re: Multiple application of LinearFilter
• From: "Lea Rebanks" <lrebanks at netvigator.com>
• Date: Tue, 7 Mar 2006 06:11:51 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

Many thanks for your note Steve.
I shall look into that
Best Regards - Lea Rebanks...

-----Original Message-----
From: Steve Luttrell
To: mathgroup at smc.vnet.net
[mailto:steve_usenet at _removemefirst_luttrell.org.uk] 
Subject: [mg64901] [mg64856] Re: Multiple application of LinearFilter

You can short-circuit this iterative filtering.

A sequence of linear filterings is itself a linear filtering, so you
could 
implement a sequence of any number of linear filterings as a single
linear 
filtering that you can deduce from the composition of the individual
linear 
filterings in the seqeunce.

Furthermore, if the linear filterings are actually convolutions (i.e.
shift 
invariant) then you can implement the sequence of linear filterings
neatly 
in Fourier space by using the convolution theorem.

I strongly urge you to read a book on signal processing, linear
filtering, 
and all that.

Steve Luttrell

"Lea Rebanks" <lrebanks at netvigator.com> wrote in message 
news:dubjps$h0t$1 at smc.vnet.net...
>
>
> Hi All,
>
> I have been using LinearFilter on my data with great success & achieve
> better results the more times I pass my data through the LinearFilter.
(
> I have had to adjust data length to maintain correct indexing with
> PadLeft - but this is not my question here.)
>
> Below is how I am applying the multiple LinearFilter.
>
> EG
>
> originaldata
>
> Data1=LinearFilter[originaldata, {1/2,1/2}];
> Data2=LinearFilter[Data1, {1/2,1/2}];
> Data3=LinearFilter[Data2, {1/2,1/2}];
>
>
> My question is - Is there a shorter way of writing multiple passes of
> the above.
>
> If there is a way, please show the code.
>
> It would be great if I could simply adjust the number of passes from
say
> three above to any number of passes to find optimum setting for data.
>
> Many thanks for your attention.
>
> Best Regards - Lea Rebanks...
>
>
>