[R] Model II regression on segmented data

plorch@zoo.utoronto.ca plorch at zoo.utoronto.ca
Fri Oct 4 05:35:46 CEST 2002

I am interested in doing Reduced Major Axis regression in R.  Has anyone 
implemented this?

I am aware of how to calculate the slope using RMA (and previous threads 
on this list about RMA), but I would like to estimate break points in 
data where there are two (or more) distinct trends.  This is 
straightforward with Ordinary Least Squares (iteratively try x values, 
set up dummy variables, find x that maximizes R^2).  But it seems like 
it would be more difficult with RMA.  The critical thing, it seems to 
me, would be how to estimate R^2 for the more complex model.   Once the 
break point is identified, it would also be nice to also estimate the 
two (or more trends).

Thanks for any help you can give.

	Dr. Patrick D. Lorch
	Zoology Dept.				W: 416-978-0172
	University of Toronto		F: 416-978-8532
	Ramsay Wright Labs		plorch at zoo.utoronto.ca
	25 Harbord St.			http://www.zoo.utoronto.ca/lrowe/plorch
	Toronto, Ontario  M5S 3G5

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