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Re: Why is my Butterworth filter so noisy?
From: |
Sergei Steshenko |
Subject: |
Re: Why is my Butterworth filter so noisy? |
Date: |
Mon, 22 Sep 2008 10:38:34 -0700 (PDT) |
--- On Mon, 9/22/08, Matthias Brennwald <address@hidden> wrote:
> From: Matthias Brennwald <address@hidden>
> Subject: Re: Why is my Butterworth filter so noisy?
> To: address@hidden, address@hidden
> Date: Monday, September 22, 2008, 10:27 AM
> On 22.09.2008, at 18:12, Sergei Steshenko wrote:
>
> > You might be interested in the following:
> >
> >
> http://www.nabble.com/ripple-in-Butterworth-filter-created-
> >
> by-'butter'-(was-"RE%3A-'long-double'-support--")-
>
> > td17092962.html#a17092962
>
> Ok. So THE recommended way of using butter.m is to not
> return the
> filter coefficients, but the have it return the poles,
> zeros, and the
> gain. So I'd to the following:
>
> [z,p,g] = butter (...)
>
> Now, how should I use z, p and g to filter my data? I
> believe I
> cannot use filter.m with these data.
>
> Matthias
There is an example script below the message, it shows how to use poles and
zeros. I mean the
http://www.nabble.com/ripple-in-Butterworth-filter-created-by-'butter'-(was-"RE%3A-'long-double'-support--")-td17092962.html#a17092962
.
Look for
# good accuracy BEGIN
and for znom (i.e. nominator in z-plane, zeros) and zdenom (denominator
in z-plane, poles) and a couple of 'for' loops - everything is very
straightforward.
Regards,
Sergei.