I would recommend that you use auglag() rather than constrOptim.nl() in the package "alabama." It is a better algorithm, and it does not require feasible starting values. Best, Ravi
-----Original Message----- From: Rainer M Krug [mailto:rai...@krugs.de] Sent: Thursday, October 01, 2015 3:37 AM To: Ravi Varadhan <ravi.varad...@jhu.edu> Cc: 'r-help@r-project.org' <r-help@r-project.org> Subject: Re: optimizing with non-linear constraints Ravi Varadhan <ravi.varad...@jhu.edu> writes: > Hi Rainer, > It is very simple to specify the constraints (linear or nonlinear) in > "alabama" . They are specified in a function called `hin', where the > constraints are written such that they are positive. OK - I somehow missed the part that, when the values x are valid, i.e. in the range as defined by the conditions, the result of hin(x) that they are all positive. > Your two nonlinear constraints would be written as follows: > > hin <- function(x, LAI) { > h <- rep(NA, 2) > h[1] <- LAI^x[2] / x[3] + x[1] > h[2] <- 1 - x[1] - LAI^x[2] / x[3] > h > } Makes perfect sense. > > Please take a look at the help page. If it is still not clear, you can > contact me offline. Yup - I did. But I somehow missed the fact stated above. I am using constrOptim() and constrOptim.nl() for a paper and am compiling a separate document which explains how to get the constraints for the two functions step by step - I will make it available as a blog post and a pdf. I might have further questions concerning the different fitting functions and which ones are the most appropriate in my case. Thanks a lot, Rainer > Best, > Ravi > > Ravi Varadhan, Ph.D. (Biostatistics), Ph.D. (Environmental Engg) > Associate Professor, Department of Oncology Division of Biostatistics > & Bionformatics Sidney Kimmel Comprehensive Cancer Center Johns > Hopkins University > 550 N. Broadway, Suite 1111-E > Baltimore, MD 21205 > 410-502-2619 > > > [[alternative HTML version deleted]] > -- Rainer M. Krug email: Rainer<at>krugs<dot>de PGP: 0x0F52F982 ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.