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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 *

...rror in MEEM(object, conLin, control$niterEM) : Singularity in backsolve at level 0, block 1 ************************************** I also fitted the same model by using SAS and winBUGS. They all worked well... Do you have any suggestions on this problem? Any reply will be appreciated! Lijuan

Hi, Sorry to bother those who are not interested in the question. I am using R to run a multiphase mixed-effects model. I simulated a data set by using the following model. And now I want to use R to estimate the parameters and compare the results with the true values. The equations of the models are as below: gf[ij]=b0[i]+b1[i]*age[ij]+b2[i]*max(0,(age[ij]-tau[i]))+e[ij] b0[i]=b00+e[i0]