From Troy.Robertson at aad.gov.au  Wed Oct 13 07:51:20 2010
From: Troy.Robertson at aad.gov.au (Troy Robertson)
Date: Wed, 13 Oct 2010 16:51:20 +1100
Subject: [Rd] Wierd nlm behaviour in 2.10.1 and 2.12.0 [Sec=Unclassified]
Message-ID: <42C7503E0B99F248B06BC65E7D2B4E020187DD725C1C@EX2K7-CCR.AAD.GOV.AU>

Hi all,

When upgrading to 2.11.1 recently I noticed different results being produced by my code.
After MUCH digging into my code I have finally narrowed it to a call to nlm().
The problem actually occurs in 2.10.1 and 2.12.0.

This can be replicated by trying the code below in some different versions of R:

FixedRemovals<-1836180125888
AbStageInitial<-2223033830403
Rates<- 0.3102445
myfunc<-function(rootM,Abund,Loss,OtherM)
     {(Loss-(rootM/(rootM+OtherM)*
      (1-exp(-(rootM+OtherM)))*
      Abund))^2}

nlm(myfunc
   ,0.001,print.level=0,fscale=0, gradtol=1E-10, stepmax = 100.0
   ,Loss=FixedRemovals
   ,Abund=AbStageInitial
   ,OtherM=Rates)

nlm(myfunc
   ,0.001,print.level=0,fscale=0, gradtol=1E-10, stepmax = 100.0
   ,Loss=FixedRemovals
   ,Abund=AbStageInitial
   ,OtherM=Rates)$estimate

Why would I be seeing a different value of 'estimate' (or any of the other returned list items)?
Originally I thought it was 2.11.1 that was giving me the grief with different output but now I see that in 2.11.1 I get the same value to each returned list item both ways.
Can anyone explain this?

Thanks

Troy
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[Rd] Wierd nlm behaviour in 2.10.1 and 2.12.0 [Sec=Unclassified]
Troy Robertson