LME() error – iteration limit reached

In specifying a crossed mixed effects model, I am trying to include interactions. However, I get the following error message:

Error in lme.formula(rate ~ nozzle, random = ~nozzle | operator, data = Flow) : 
nlminb problem, convergence error code = 1
message = iteration limit reached without convergence (10)

The model has the following:
1. 3 nozzle types (fixed effect)
2. 5 operators, each with 3 repeat measures on fuel flow from the 3 nozzle types.

I was asked to include the interaction between nozzle type and operator in the model.
This is my code for the model:

flow.lme <- lme(rate ~ nozzle, error= nozzle|operator, data=Flow)

Why would I get this error message??

Answer

I haven’t heard of the error argument to lme and I don’t see it in the documentation. Are you sure that isn’t a typo? But, to answer the question you asked:

Try ?lmeControl

Setting the maxIter, msMaxIter, niterEM, and/or msMaxEval arguments to higher values than the default may fix this. Capture the output from lmeControl to an object and then pass that object to the control argument of lme.

Or…

The new default optimizer lme uses is flaky. Half the time these sorts of problems get solved for me when I change it back to the old optimizer. You do this by setting the opt argument for lmeControl to 'optim'.

So, putting it together:

ctrl <- lmeControl(opt='optim');
flow.lme <- lme(rate ~ nozzle, error= nozzle|operator, control=ctrl, data=Flow);

Attribution
Source : Link , Question Author : Tal Bashan , Answer Author : f1r3br4nd

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