From help-octave-request at bevo dot che dot wisc dot edu  Fri Jan  8 15:05:50 1999
Subject: Re: How do I build low pass filter?
From: John Day <jday at csihq dot com>
To: Thomas Hoffmann <hoffmann at ehmgs2 dot et dot tu-dresden dot de>,         help-octave@bevo.che.wisc.edu
Date: Fri, 08 Jan 1999 15:56:39 -0500

Hi,

Here are some ways to 'despeckle' data, depending on the nature of
the noise:

1. 'Salt and pepper' spikes are often easily removed by using a median
filter.
2. A low-pass filter will attenuate spikes. Be careful on choice of
filter, some can produce more artifacts than they eliminate. I usually
use a Gaussian filter to get best results.
3. 'Detect' spikes by integrating their energy and threshold them out.
Of course this won't work if spikes are highly energetic.

Hope that helps.

-jday

At 01:22 PM 1/8/99 +0100, Thomas Hoffmann wrote:
>Can anybody tell how I should proceed to filter out some "spikes"
>from a vector of data using Octave?
>
>If I visualize the vector I can see its basically regular structure which
>is disturbed by some zig-zags which I would like to eliminate (mainly to
>be able to find meaningful extrema of the basic structure).
>
>Thomas.
>
>
>