[R] how to set the starting value in lme

[Daniel Kaschek]

Hi Jia,

in order to test if the failing parameter estimation really has to do
with wrong initial values, you could first simulate data with your mixed
effects model. Just assume parameters, produce a data set with these
parameters, add noise and look if you can estimate the parameters
correctly with varying initial guesses.



On Tue, 2011-03-15 at 12:34 -0700, jia liu wrote: 
> Hi,
> When I fit the mixed-effects model by lme, I got theconvergence error code = 1
> message = iteration limit reached without convergence (9). Even after I increase the iteration numbers, it still did not work. The only way I found to avoid the error message is to increase thenumber of iterations for the EM algorithm, which need to be at least 1100. But the weird thing is that the correlation between two random coefficients is always around 1, which is not true. So I am thinking the error should be related with the improper starting value. But I do not know how to set up my desired starting value in lme function. Are there anybody know it? Or met the same problem with me before and know how to avoid the error? Thank you for your help.
> Bests,
> Jia
> 
> 
>       
> 	[[alternative HTML version deleted]]
> 
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-- 
Daniel Kaschek
Physikalisches Institut, Freiburg
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79104 Freiburg

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