The option 2 works. Thanks. Hanna 2015-12-09 16:24 GMT-05:00 Bert Gunter <bgunter.4...@gmail.com>:
> 1. Don't know, but, assuming I understand you correctly, probably not. > > 2 Note (subject to my understanding again) that you can rephrase your > query as fitting a 4 parameter logistic to all the data together with > a grouping factor to indicate the separate curves, allowing two of the > parameters (e.g. ED50 and slope) to vary by group. You can then use > standard nonlinear fitting (e.g. via the optimx package) to fit the > model. Note that you will have to specify 2c +2 starting values for c > curves. With c "large" (?whatever that means), this may make > convergence tricky. > > If you care to reply, please do so to the list, not to me. > > Cheers, > Bert > > > > > Bert Gunter > > "The trouble with having an open mind is that people keep coming along > and sticking things into it." > -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) > > > On Wed, Dec 9, 2015 at 12:27 PM, li li <hannah....@gmail.com> wrote: > > Hi all, > > In drc package, is there a function which can be used to fit restricted > > 4PL curves? For example, we restrict two 4PL curves have the same lower > and > > upper asymptotes? > > Thanks for the help in advance! > > Hanna > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > 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. > [[alternative HTML version deleted]] ______________________________________________ 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.
