User control of gradtol argument

questions concerning anlysis/theory using program DENSITY and R package secr. Focus on spatially-explicit analysis.

User control of gradtol argument

Postby howeer » Mon Feb 28, 2011 4:11 pm

I notice that when I fit secr models, the last few hundered iterations of the minimization procedure seem to have all the same LL and parameter values (within the # of digits displayed). I was wondering if I could reduce computation time without sacrificing reliability of the results by increasing gradtol (argument of function nlm) by an order of magnitude or so. I might try fitting the same model with gradtol at the default (1e-6), and at higher values (1e-4 or 5), and checking for differences in the results. Can I simply include the gradtol argument in the call to, similarly to stepmax? And, would you recommend against increasing gradtol?
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Re: User control of gradtol argument

Postby murray.efford » Mon Apr 25, 2011 12:19 am

Sorry for the 2-month delay - it seems phidot had stopped notifying me of postings. I guess you've answered your own question by now. The answer is, yes the 'dots' arguments are passed on to nlm (the default maxization function). I would be careful, though. At least, check any final result by running with the default tolerance.
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