[R] syntax of nlme
thomas.wutzler at web.de
Mon Sep 11 17:41:52 CEST 2006
How do I specify the formula and random effects without a startup object
? I thought it would be a mixture of nls and lme.
after trying very hard, I ask for help on using nlme.
Can someone hint me to some examples?
I constructed a try using the example from nls:
#variables are density, conc and Run
#all works fine with nls
DNase1 <- subset(DNase, Run == 1 )
fm2DNase1 <- nls( density ~ 1/(1 + exp((xmid - log(conc))/scal)),
data = DNase1,
start = list(xmid = 0, scal = 1),
trace = TRUE)
#Now I want to do a mixed model with covariate Run
#how is the syntax?
DNase12 <- subset(DNase, Run == 1 | Run == 2)
fm2DNase1 <- nlme( density ~ 1/(1 + exp((xmid - log(conc))/scal)),
data = DNase12,
fixed = conc ~ 1,
random = Run ~ 1,
start = list(xmid = 0, scal = 1)
#gives: Error in eval(expr, envir, enclos) : object "xmid" not found
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