View Full Version : Re: 'Normalisation' of curves

Ingram Murray
02-16-1999, 07:57 AM
Dear subscribers,
I am interested in the techniques used by the biomechanical
community for 'normalising' or 'registering' the curves obtained,
of joint angle, force or moment variation during human motion
analysis studies.
The aim of this process is to overcome the offsets between
structurally similar curves due to differences in, for instance, the
speed of performance of the movements between subjects.
This then allows 'average' curves to be calculated without
removing real properties of these curves.
Methods for this process are described in:

A. Kneip and Th. Gasser (1992). Statistical tools to analyze data
representing a sample of curves. Annals of Statistics 20 1266-1305.

K. Wang and Th. Gasser (1997). Alignment of curves by dynamic
time warping. Annals of Statistics 25, 1251-1276.

K. Wang and Th. Gasser (1996). Asymptotic and Bootstrap
confidence bounds for structural average of curves.
submitted to Annals of Statistics.

and I am also aware of the use of polynomial expansions and splines
or Fourier analysis for the normalising of data to one hundred
percentage points.

I was wondering if subscribers could express their opinions on the
merits or otherwise of such techniques, or suggest alternatives.
I will submit a summary of any replies I receive.

Many Thanks

Ingram Murray
Room G32
Stephenson Building
University of Newcastle upon Tyne
Newcastle upon Tyne

Tel: 0191 222 6000 ext.6193
Fax: 0191 222 8600
email: i.a.murray@ncl.ac.uk
www: http://www.ncl.ac.uk/crest/IMpers

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