On Thu, 23 Dec 2010, John Sorkin wrote:
Windows Vista
R 2.10 - I know it is old, I will update later today.
How might I perform a piece-wise linear regression where two linear
segments are separated by a single knot? In addition to estimating the
slopes of the two segments (or the slope in one segment and the
difference between the slope of the first and second segment), I would
like the analysis to select the optimum knot. My first analysis will
contain a single dependent and a single independent variables.
Subsequent analyses will add additional independent variables to
determine the effect on the results of adjusting for potential
confounding.
Have a look at the "segmented" package, introduced in R News in
http://www.R-project.org/doc/Rnews/Rnews_2008-1.pdf
Best,
Z
Thank you,
John
John David Sorkin M.D., Ph.D.
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)
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