-------- Original Message --------
Subject: Re: outlines analysis Fourier coefficients
Date: Wed, 27 Feb 2008 06:37:32 -0800 (PST)
From: Matthew Burton-Kelly <[EMAIL PROTECTED]>
To: [email protected]
References: <[EMAIL PROTECTED]>
Hello all,
The quoted message is from a couple months back, but I would like to
clarify for my own sanity. I am attempting to calculate disparity
based on elliptical Fourier coefficients--am I correct in thinking
that I can use MD=Tr{S}* on my elliptical Fourier coefficients in the
same way I could on partial warp scores?
*Morphological Disparity = Trace(variance-covariance matrix)
Thanks,
Matt Burton-Kelly
On 25 Nov, 2007, at 9:36 AM, morphmet wrote:
The same considerations apply to any multivariate study (conventional
variables, partial warp scores, or scores on Fourier harmonics). One
can
use exploratory methods such as PCA or cluster analysis with any
sample
size but in order use methods that look at difference among groups
relative to within-group variability one needs the degrees of
freedom of
the within-group covariance matrix to be greater than the number of
variables. With fewer observations the within-group covariance matrix
will be singular. This rule gives a minimum sample size but for
reliable
results the sample size should, of course, be much larger. This makes
the use of a number of standard multivariate methods impractical when
using many harmonics or many landmarks so that less powerful methods
have to be used.
------------------------
F. James Rohlf, Distinguished Professor
Ecology & Evolution, Stony Brook University
www: http://life.bio.sunysb.edu/ee/rohlf
-----Original Message-----
From: morphmet [mailto:[EMAIL PROTECTED]
Sent: Sunday, November 25, 2007 6:44 AM
To: morphmet
Subject: outlines analysis Fourier coefficients
Dear morphometricians.
I would like to know, if it is possible...
How to calculate the number of harmonics, for the estimation of
Fourier
coefficients, depending the number of individuals sampled.
Some formulae.
I know this formulae (k-1)/2 or (k/2, K=numer of points on the
outlines.
I know that the number of harmonics depends on the degree of
recostrucion of the original structure, but what about the number of
individual.
Thanks
Ang�lica Cuevas
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-----------------------------
Matthew Burton-Kelly
Graduate Student
Department of Geology and Geological Engineering
University of North Dakota
(802) 922-3696
[EMAIL PROTECTED]
http://uweb.und.nodak.edu/~matthew.burton.kelly/
--------------------------------------------
"About thirty years ago there was much talk that geologists ought only
to observe and not theorize; and I well remember someone saying that
at this rate a man might as well go into a gravelpit and count the
pebbles and describe the colors. How odd it is that anyone should not
see that all observation must be for or against some view if it is to
be of any service!"
-Charles Darwin, in an 1861 letter to Henry Fawcett.
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For more information visit http://www.morphometrics.org
