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Re: Re: Multiple application of LinearFilter

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

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

-----Original Message-----
From: Steve Luttrell
To: mathgroup at
[mailto:steve_usenet at] 
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
implement a sequence of any number of linear filterings as a single
filtering that you can deduce from the composition of the individual
filterings in the seqeunce.

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

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

Steve Luttrell

"Lea Rebanks" <lrebanks at> wrote in message 
news:dubjps$h0t$1 at
> 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
> three above to any number of passes to find optimum setting for data.
> Many thanks for your attention.
> Best Regards - Lea Rebanks...

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