constraining correlation = 1

From: Lutz Ph. Breitling <lutz.breitling_at_GMAIL.COM>
Date: Tue, 28 Nov 2006 17:13:08 +0000

Dear All,

I am trying to test the hypothesis that the additive genetic
correlation in my bivariate trait animal model is different from 1.

For the significance of its difference from 0, I can simply specify a
starting value of 0.0 for the covariance term in the variance
structure specification and use a qualifier like !GUFU to keep it
fixed at 0.

But I don't find a way to fix the correlation = 1. Constraining the
two variances and their covariance to be equal (using a VCC line
-depending on the exact model- like 13 14 15) won't converge in any
case. Essentially, this is also asking too much, since for cor12=1, it
is not really necessary to have var1=var2, right?

Are there any options that I'm not aware of, or does my approach look
simply wrong altogether? Any comments would be highly appreciated.

Many thanks-

Lutz Ph. Breitling, Marie Curie EST Research Fellow
Integrative & Comparative Biology (Irene Manton 8.93e)
University of Leeds, LS2 9JT Leeds/UK
Received on Sun Nov 28 2006 - 17:13:08 EST

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