🚀 go-pugleaf

In article <73276@netnews.upenn.edu>, jim@heart.circ.upenn.edu (Jim Streicher) writes:
>
>I am looking for source code examples (C, fortran, or pascal)
>of digital filtering. 
>
>None of the "classic" books I have been referred to give any
>program examples.
>
>Specifically, I need a low pass filter (30-40 hz cutoff) for
>a data set sampled at 100 hz. 
>
...
If this is not a real-time problem, the easiest way and the one that gives you
the most control is to filter in the frequency domain.  There you can create
your filter to have the exact characteristics you want, multiply it by the
data, and transform the result back to the time domain.  It is a good idea to
look at the impulse response of your filter (the absolute value of its
transform) to see that it does not produce spurious ringing in the filtered
data or otherwise unacceptably distort sudden changes. This method is treated
inadequately or not at all in the few texts I have looked at.  I don't have any
actual code you could use, sorry. 

Dr. David L. Matthews, IPST, Univ. of Maryland, College Park MD 20742-2431 
Telephone  (301)405-4830	Internet   dmatthews@uap.umd.edu
FAX 	   (301)314-9363	NSI/SPAN   UMDUAP::DMATTHEWS