[R] a question about using nlme
Lijuan Wang
lw7s at cms.mail.virginia.edu
Wed Jul 28 03:30:38 CEST 2004
Hi,
I am using Splus to run a multiphase mixed-effects model.
The quations of the models are as below:
gf[ij]=b0[i]+b1[i]*age[ij]+b2[i]*max(0,(age[ij]-tau[i]))^2+e[ij]
b0[i]=b00+e[i0]
b1[i]=b10+e[i1]
b2[i]=b20+e[i2]
tau[i]=tau+e[i3]
i: 1,2,...,100 subjects
j: 1,2,...,6 occasions
The main scripts of Splus is:
simu1<-groupedData(gf~age|id)
simu.nlme<-nlme(gf~(b0 + b1 * age + b2 *
max(0,(age-tau))^2),data=simu1,fixed=list(b0~1,b1~1,b2~1,tau~1),
+
random=list(b0~1,b1~1,b2~1,tau~1),start=c(b0=4,b1=5.32,b2=-5.29,tau=14.8))
But it seems like that there are some errors in it.
Error in .C("mixed_EM",: Singularity in backsolve at level
2, block 1
I think maybe there is something wrong in my scripts,
could you help me to find it?
Thanks a lot
Peggy
More information about the R-help
mailing list