[R] optim() non-finite finite-difference value

[Spencer Graves]

	  I just encountered that myself using optim in S-Plus 6.1.  For a 
certain set of parameter values, the function I wanted to minimize 
returned NaN (not a number).  To fix this problem, I set a trace with 
something like options(trace=99) using, I think, method = "CG".  This 
printed out all the parameter values tested including the one that 
generated the offense.  I then took that set of parameter values to the 
function to be optimized and figured out a way to limit the range of the 
computations.  I used a construct like the following:

	  good.num.limit = c(.Machine$double.xmin, .Machine$double.xmax)^(1/3)

Then I constrained certain positive numbers to lie within these bounds, 
thereby avoiding 0 and Inf.

	  Then I tested the result using method = "Nelder-Mead", "BFGS", and 
"CG".  For my particular installation, for some unknown reason, 
Nelder-Mead bombed S-Plus, BFGS returned a nonsense answer, but CG was 
sensible.  Just a few minutes ago, I restarted my (several hour) job.  I 
think it should be more likely to finish now.

	  hope this helps.
	  spencer graves

Werner Bier wrote:
> Dear all,
>  
> I am using the optim() function which it stops with the following error messagge:
>  
> error in optim(...)  non-finite finite-difference value
>  
> I was wondering if somebody might suggest me a way to fix it please.
>  
> Thanks in advance to all of you.
> Kind regards,
> Tom
> 
> __________________________________________________
> 
> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html