View Full Version : Reposting of Call for data smoothing help

Robert Newton
02-04-1993, 12:03 PM
Dear fellow networkers,

I must apologise for reposting this call for assistance. I am afraid that our
mail spooler erased the excellent replies that I had received over the last
few days. This occurred before I could store them in my own file. I would
greatly appreciate it if those who posted replies could resend them. Of the
many replies I did receive eight were from people requesting that I forward a
summary of the information on to them. I will send this to all Biomch-L as
soon as I compile the replies.

************************ Previous Request **********************************
I am developing a research project which involves the use of a rotary encoder
to provide displacement data to a resolution of 0.5 mm in 3.0 m at a frequency
of 500 Hz. I wish to derive velocity and acceleration data and have been using
a Butterworth filter for smoothing and differentiation of kinematic data which
is essentially parabolic in path. I would be most appreciative of any help
that can be provided as to:

1. Is the Butterworth a suitable filter or is there a better
alternative? I believe I have implemented a 4th order Recursive Butterworth?

2. Can anyone tell me what coefficients I should use for the terms in
the filter to produce a given cutoff frequency or is there a reference which
would list such information?

3. Can anyone direct me to a good review on data filtering in
biomechanics? In particular I need information on the actual
smoothing/differentiation algorithms. Code examples in C, Fortran etc would be
very helpful.

4. I would appreciate it if anyone could email me sample source code
of any smoothing/differentiation routines.
************************************************** *************************

Thankyou in advance for any assistance that you can provide. It is
greatly appreciated. Once again I apologise if you took the time to reply but
I did not receive it. Please send again.


Robert Newton Internet: rnewton@alsvid.une.oz.au
Lecturer in Biomechanics ACSnet: rnewton@alsvid.une.oz
University of NewEngland,
Northern Rivers Phone: +61 (066) 203762
P.O. Box 157
Lismore NSW Australia