Thanks to Peter for noting that the numerical derivative part of code doesn't
check bounds in optim().
I tried to put some checks into Rvmmin and Rcgmin in optimx package (they were
separate packages before, and
still on CRAN), but I'm far from capturing all the places where numerical
derivative steps can go outside bounds.
And if you have a "production" problem where you are going to run a given
optimization over a lot of cases, I'd
strongly suggest that you write your own derivative code, even if it is a
numerical approximation. In the case of
a specialized derivative code e.g., part analytic, part numeric, with bounds
checking, I'll be willing
to kibbitz, but suggest off-list until something is working, in which case it
is probably at least worth
a vignette, as this sort of situation seems to pop up at least once a year and
a good example would really
be helpful to guide the process. I'm reluctant to prepare an artificial example
because, well, it will be
artificial and not capture the sort of details that have to be addressed.
Best, JN
On 2020-08-11 3:48 a.m., peter dalgaard wrote:
> This stuff is of course dependent on exactly which optimization problem you
> have, but optimx::optimr is often a very good drop-in replacement for optim,
> especially when bounds are involved (e.g., optim has an awkward habit of
> attempting evaluations outside the domain when numerical derivatives are
> needed).
>
> You might want to look at the last examples in ?stats4::mle (in R 4.x.x)
>
> -pd
>
>> On 10 Aug 2020, at 22:08 , Roy Mendelssohn - NOAA Federal via R-help
>> <r-help@r-project.org> wrote:
>>
>> I am running a lot of optimization problems, at the moment using 'optim'
>> ('optim' is actually called by another program). All of the problems have
>> variables with simple upper and lower bounds, which I can easily transform
>> into a form that is unconstrained and solve using 'BFGS'. But I was
>> wondering is if it is more robust to solve the problem this way, or to use
>> L-BFGS-B instead.
>>
>> Also how much difference can it make using 'optimx' instead 'optim'? The
>> program I am using (KFAS) allows this, I just have to do some extra
>> programming to use it.
>>
>> Thanks,
>>
>> -Roy
>>
>>
>>
>> **********************
>> "The contents of this message do not reflect any position of the U.S.
>> Government or NOAA."
>> **********************
>> Roy Mendelssohn
>> Supervisory Operations Research Analyst
>> NOAA/NMFS
>> Environmental Research Division
>> Southwest Fisheries Science Center
>> ***Note new street address***
>> 110 McAllister Way
>> Santa Cruz, CA 95060
>> Phone: (831)-420-3666
>> Fax: (831) 420-3980
>> e-mail: roy.mendelss...@noaa.gov www: https://www.pfeg.noaa.gov/
>>
>> "Old age and treachery will overcome youth and skill."
>> "From those who have been given much, much will be expected"
>> "the arc of the moral universe is long, but it bends toward justice" -MLK Jr.
>>
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