[R-sig-ME] Convergence problem

[Boulanger, Yan]

Hi folks, 

I'm new to nlme and I'm trying to fit a somewhat simple mixed regression model:

PICE.MAR_tree_dbh_model <- lme(log(dbh_tree) ~ Temp+Prec+I(Prec/age_tree)+I(Temp/age_tree), weights = varPower(form =~fitted(.)) , random= ~1|plot_name, data=PICE.MAR_tree, method="REML")


However, convergence is never reached:

  (Error in lme.formula(log(dbh_tree) ~ Temp + Prec + I(Prec/age_tree) +  : 
  maximum number of iterations (lmeControl(maxIter)) reached without convergence)

 Here's the structure of my data. dbh_tree and age_tree is measured on the tree which is nested in plot_name (random effect). Temp and Prec are measured at the plot level. I have also a very unbalanced setup with sometimes only 1 tree per plot and others where there are as much as 150 trees. Maybe the syntax is not right.

Thank you!

Yan Boulanger




>Yan Boulanger, Postdoctoral Visiting Fellow
>Ressources Naturelles Canada, Canadian Forest Service
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