I'm running some glmms and when I run the code: Model5 <- glmer.nb(Count ~ Light + (1|Site), data = dframe5)
I get the error messages:
1: In checkConv(attr(opt, "derivs"), opt$par, ctrl = control$checkConv, :
unable to evaluate scaled gradient
2: In checkConv(attr(opt, "derivs"), opt$par, ctrl = control$checkConv, :
Model failed to converge: degenerate Hessian with 2 negative eigenvalues
It was suggested that I could get around these messages by restarting the model from a different point using the code:
ss <- getME(Model5,c("theta","fixef"))
ss
Model5b <- update(Model5,start=ss)
This has stopped me from getting convergence errors and given me normal-seeming results but I wanted to double check that this is an OK thing to do.