[R-sig-ME] novel correlation structure for nlme package, lme function

[Edland, Steven]

Hello my programmer friends.  I am wondering if anyone has written a corStruct for this lme call:

lme(y~time*group, random= ~time|id)

In this call, the covariance structure implied by (time|id) is assumed constant across groups.  We would like to model these random effects separately in the two groups.

Motivation:  In a clinical trail with an _effective_ treatment, response to treatment will  be variable (variance of the random slopes will be greater in the treatment arm).


Thank you in advance for any thoughts where I might find such a corStruct.

Steve Edland & Yu Zhao


Sincerely,
Steve Edland

Steven D. Edland, Ph.D.
Professor
Dept. of Family Medicine & Public Health
Dept. of Neurosciences
University of California, San Diego
9500 Gilman Dr. M/C 0948
La Jolla, CA 92093-0948
http://biostat.ucsd.edu/sedland.htm

	[[alternative HTML version deleted]]