Re: Re: Butterworth filter
- To: mathgroup at smc.vnet.net
- Subject: [mg108501] Re: [mg108462] Re: Butterworth filter
- From: Sseziwa Mukasa <mukasa at jeol.com>
- Date: Sat, 20 Mar 2010 02:46:30 -0500 (EST)
- References: <hnkfa8$po0$1@smc.vnet.net> <hnl0ln$6uq$1@smc.vnet.net> <201003190746.CAA08409@smc.vnet.net>
On Mar 19, 2010, at 3:46 AM, Paul Floyd wrote: > On Mon, 15 Mar 2010 10:03:35 +0000 (UTC), Nasser M. Abbasi > <nma at 12000.org> wrote: >> "Luigi B" <l.balzano at gmail.com> wrote in message >> news:hnkfa8$po0$1 at smc.vnet.net... >>> Dear All, >>> I have a table {{x,y}} of measured data with significant noise. >>> I am not into signal processing and I would like to filter this >>> table >>> with a Butterworth type of filter. >>> Does anyone have a suitable routine? (That would allow changin the >>> order of the filter as well, like the function 'butter' in another >>> system). Perhaps you're not getting many responses because your question is somewhat unclear. A Butterworth filter is typically used for analog signal processing, but your data is digitized so you'd have to use a digital filter. One can digitize Butterworth filters but they don't have all the properties of an analog Butterworth filter, furthermore, it is trivial to implement an ideal low pass filter with superior performance to a Butterworth for digitized data: Fourier transform the signal, zero out all values greater than the desired cut off frequency, Inverse Fourier transform to get the filtered signal. Without further information about your data whether this is appropriate or not, but if the goal is a low pass filter why insist on a Butterworth? >> >> This is not much help to you now, but there used to be a >> Mathematica add-on >> application called signals and systems which had this and more >> filters: >> >> http://documents.wolfram.com/applications/signals/ >> FilterAnalysisandDesign.html >> >> Too bad this application is no longer available. > > Hi > > I'd be interested in this as well. > > Do you know who produced it, and whether it'd be possible to get it > working again with Mathematica 7? The Digital Image Processing package has some digital filter design features, the Control Systems package can handle analog filters, but admittedly not in the way signal processing is usually done. Regards, Sseziwa
- References:
- Re: Butterworth filter
- From: Paul Floyd <root@127.0.0.1>
- Re: Butterworth filter