I'm sorry, I have not followed this thread, but I wonder if you have
considered library(sem), "structural equations modeling"? "Errors in
variables" problems are the canonical special case.
Also, have you done a search of "www.r-project.org" -> search -> "R
site search" for terms like "errors in variables regression"? This just
led me to "ODRpack", which is NOT a CRAN package but is apparently
available after a Google search. If it were my problem, I'd first try
to figure out "sem"; if that seemed too difficult, I might then look at
"ODRpack".
Also, have you read the posting guide!
http://www.R-project.org/posting-guide.html? This suggests, among other
things, that you provide a toy example that a potential respondant could
easily copy from your email, test a few modifications, and prase a reply
in a minute or so. This also helps clarify your question so any
respondants are more likely to suggest something that is actually useful
to you. Moreover, many people have reported that they were able to
answer their own question in the course of preparing a question for this
list using the posting guide.
hope this helps. spencer graves
Eric-Olivier Le Bigot wrote:
I'm interested in this "2D line fitting" too! I've been looking,
without success, in the list of R packages.
It might be possible to implement quite easily some of the formalism
that you can find in Numerical Recipes (Fortran 77, 2nd ed.), paragraph
15.3. As a matter of fact, I did this in R but only for a model of the
form y ~ x (with a given covariance matrix between x and y). I can send
you the R code (preliminary version: I wrote it yesterday), if you want.
Another interesting reference might be Am. J. Phys. 60, p. 66 (1992).
But, again, you would have to implement things by yourself.
All the best,
EOL
--
Dr. Eric-Olivier LE BIGOT (EOL) CNRS Associate Researcher
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Kastler Brossel Laboratory (LKB) http://www.lkb.ens.fr
Université P. & M. Curie and Ecole Normale Supérieure, Case 74
4 place Jussieu 75252 Paris CEDEX 05 France
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On Wed, 25 May 2005, Jacob van Wyk wrote:
I hope somebody can help.
A student of mine is doing a study on Measurement Error models
(errors-in-variables, total least squares, etc.). I have an old
reference to a "multi archive" that contains
leiv3: Programs for best line fitting with errors in both coordinates.
(The date is October 1989, by B.D. Ripley et al.)
I have done a search for something similar in R withour success. Has
this been implemented in a R-package, possibly under some sort of
assumptions about variances. I would lke my student to apply some
regression techniques to data that fit this profile.
Any help is much appreciated.
(If I have not done my search more carefully - my apologies.)
Thanks
Jacob
Jacob L van Wyk
Department of Mathematics and Statistics
University of Johannesburg APK
P O Box 524
Auckland Park 2006
South Africa
Tel: +27-11-489-3080
Fax: +27-11-489-2832
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