[R] piecewise regression using nlme function

Carlson, Erik A (GE, Research)
Thu, 07 Jan 2010 20:46:57 -0000

Is a 95% CI on a breakpoint fixed effect legitimate when the nonlinear
equation is continuous but not differentiable at the breakpoint?

I used the nlme to generate a non-linear mixed-effects piecewise model
with initial slope zero prior to an unknown breakpoint. It did give a
95% CI for the breakpoint.

Thanks
Erik

whole model is complex, but here is the simple equation used:

dr.hockey<-function(a,b,x,brk){
 a+ifelse(x<=brk,0,b*(x-brk))}



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