Good R-users,
   
  I have difficulties accessing the variance components for an lme fit when the variance covariance matrix of the random effects is not positive definite. 
   
  For example, i fit the following model:
   
  ggg <- lme (ST~ -1 + as.factor(endp):Z.sas + as.factor(endp), data=dat2a,
  random=~-1 + as.factor(endp) + as.factor(endp):Z.sas|as.factor(trials),
  correlation = corSymm(form=~1|as.factor(trials)/as.factor(id)), weights=varIdent(form=~1|endp))
   
  intervals(ggg, which="var-cov")
   
  when i try to access the variance components using  the 'intervals' function i get the following error message:
   
  "Error in intervals.lme(ggg, which = "var-cov") : 
  Cannot get confidence intervals on var-cov components: Non-positive definite approximate variance-covariance"
   
  Is there a way out of this? or better still
  Is there another function through which i can access these variance components other than the intervals function?
  
Kind regards
  Pryseley

			
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