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2010 Jul 21
0
Piecewise regression using lme()
...,t=1:65,group=as.factor(group)) the model I'd like to fit is: y_t= (beta_01+beta_11*t+error_1)*(group==1)+(beta_02+beta_12*t+error_2)*(group==2)+(beta_03+beta_13*t+error_3)*(group==3) It looks like a mixed effects model were the fixed effect are the piecewise linear regression parts (beta_0i+beta_1i*t) and the random effects are the variance components error_i. The problem is that I can't find the way the write this model correctly using the lme() function of the package nlme. I can't remove the global intercept and the global variance component. Here's what I tried: #1 Using a...