Refer to the CRAN "Optimization" task view, please. That is a much more appropriate place to begin than posting a query here.
All numerical optimizers only produce local optima. -- Bert On Thu, Nov 10, 2011 at 11:24 AM, Dimitri Liakhovitski < dimitri.liakhovit...@gmail.com> wrote: > Just to add: > > I also experimented with the starting parameters (par) under optim, > especially with the second one. I tried 1, 10, 100, 1000, etc. > When I tried 100,000,000 then I got a somewhat better solution (but > still not as good as in Excel). However, under message it said: > > "ERROR: ABNORMAL_TERMINATION_IN_LNSRCH" > > Dimitri > > On Thu, Nov 10, 2011 at 1:50 PM, Dimitri Liakhovitski > <dimitri.liakhovit...@gmail.com> wrote: > > Hello! > > > > I am trying to create an R optimization routine for a task that's > > currently being done using Excel (lots of tables, formulas, and > > Solver). > > However, otpim seems to be finding a local minimum. > > Example data, functions, and comparison with the solution found in > > Excel are below. > > I am not experienced in optimizations so thanks a lot for your advice! > > Dimitri > > > > ### 2 Inputs: > > > IV<-data.frame(IV=c(0,6672895.687,13345791.37,20018687.06,26691582.75,33364478.44,40037374.12,46710269.81,53383165.5, > 60056061.18,66728956.87,73401852.56,80074748.24,86747643.93 > ,93420539.62,100093435.3,106766331,113439226.7,120112122.4,126785018.1,133457913.7,140130809.4,146803705.1,153476600.8,160149496.5,166822392.2,173495287.9,180168183.5,186841079.2,193513974.9,200186870.6)) > > DV<-data.frame(DV=c(0,439.8839775,829.7360945 > ,1176.968757,1487.732038,1767.147276,2019.49499,2248.366401 > ,2456.78592,2647.310413,2822.109854,2983.033036,3131.661246,3269.352233, > 3397.276321,3516.446162 > ,3627.741311,3731.928591,3829.679009,3921.581866,4008.156537,4089.862363, > 4167.106955,4240.253215,4309.625263,4375.513474,4438.178766 > ,4497.856259,4554.75841,4609.077705,4660.988983)) > > > > ## Function "transformIV" transforms a data frame column "IV" using > > parameters .alpha & .beta: > > ## It returns a data frame column IV_transf: > > transformIV = function(.alpha,.beta) { > > IV_transf <- as.data.frame(1 - (1/exp((IV/.beta)^.alpha))) > > return(IV_transf) > > } > > > > ### Function "mysum" calculates the sum of absolute residuals after a > > regression with a single predictor: > > mysum<- function(myIV,myDV){ > > regr<-lm(myDV[[1]] ~ 0 + myIV[[1]]) > > mysum<-sum(abs(regr$resid)) > > return(mysum) > > } > > > > ### Function to be optimized; > > ### param is a vector of 2 values (.alpha and .beta) > > myfunc <- function(param){ > > myalpha<-param[1] > > mybeta<-param[2] > > IVtransf<-transformIV(myalpha, mybeta) > > sumofdevs<-mysum(myIV=IVtransf,myDV=DV) > > return(sumofdevs) > > } > > > > # Optimizing using optim: > > myopt <- optim(fn=myfunc, par=c(0.1,max(IV)), method="L-BFGS-B", lower=0) > > (myopt) > > myfunc(myopt$par) > > ## Comparing this solution to Excel Solver solution: > > myfunc(c(0.888452533990788,94812732.0897449)) > > > > -- > > Dimitri Liakhovitski > > marketfusionanalytics.com > > > > > > -- > Dimitri Liakhovitski > marketfusionanalytics.com > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.