start values for random effects in nlme

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start values for random effects in nlme

Jos Lommerse
Hi Lindsey,

Yeah, I do realize that this answer gets to you 12 years too late, however, it may be helpful to others in future.
I have been struggling with the same issue. When analysing the source code (
I found out that the E matrix needs rownames referring to the random effect of each group in the dataset, something like:
rownames(E) <- c("subjectname1","subjectname2","subjectname3",.....).
Then your code should run perfectly OK.


data <- data.frame(a=c(1,2,3,4,5,1,2,3,4,5,1,2,3,4,5),

# Random effect matrix E:
E <- as.matrix(c(-0.1,0.2,0.3))
rownames(E) <- c('X','Y','Z')
fm1 <- nlme(b ~ par1*a + par2*exp(IIV),
            data = data,
            fixed = list(par1 ~ 1, par2 ~ 1),
            random = IIV ~ 1 | ID,
            start = list(fixed = c(1,1), random= E))

Kind regards,
Jos Lommerse, Certara

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