[R] lme convergence failure within a loop

[Daniel Malter]

I am not an expert in this. But try try()   :)

hth,
Daniel


Sam Nicol wrote:
> 
> Hi R-users,
> 
> I'm attempting to fit a number of mixed models, all with the same 
> structure, across a spatial grid with data points collected at various 
> time points within each grid cell. I'm trying to use a 'for' loop to try 
> the model fit on each grid cell. In some cells lme does not converge, 
> giving me the error:
> 
> Error message: In lme.formula(logarea ~ year + summ_d, data = grid2, 
> random = ~year +  :
>    nlminb problem, convergence error code = 1
>    message = iteration limit reached without convergence (9)
> 
> When I get the error, the program aborts, and my loop stops.
> 
> I'm not too worried about the error, as a generic mixed model structure 
> may not be the best fit for every cell. I expect the optimization to 
> fail in some places. I want to be able to detect when the algorithm has 
> failed to converge automatically, so that I can continue my loop and 
> record the places where the model does fit. I've used the lmeControl 
> method with returnObject=TRUE options to allow me to continue looping, 
> however I want to be able to flag the places where the convergence 
> failed so that I can reject these gridcells and not mistakenly claim 
> that the model fits at these points. Is there a way to do this?
> 
> My example code shows the relevant lines of code-- what I'm hoping for 
> is a way to determine that the convergence failed and record this as a 
> boolean value, or something similar.
> 
> Thanks,
> 
> Sam Nicol
> 
> 
> 
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