Marie didier <mariedidier1 <at> gmail.com> writes: > I am a fresh user of R and I already face to problems that I don't > understand. > In the use of the function nls(), I systematically have an error message : > "Singular gradient matrix at initial parameters estimates". > I tried to use nls() on a set of data that I subseted from a bigger matrix > data. I wish to fit a gaussian on these points (spectrum) and draw this fit > on the plot. > Is this possible? Why do I always have this error message when using nls() ? > > Thank you for your answers, and don't make fun of me :) because, as I said, > I am a fresh novice :) >
We won't make fun of you, but we will chide you for not giving us enough information to help you solve your problem. "Singular gradient matrix at initial parameter estimates" means that there is a 'flat' or nearly flat direction in parameter space at the point where you tried to start the optimization. This can be a symptom of: * a model with unidentifiable (i.e. perfectly correlated) parameters * bad choices of starting parameters Please read the Posting Guide (referenced at the bottom of every post) and try again. What are the *specific* R commands you are trying to run? Can you give us a reproducible example? Ben Bolker ______________________________________________ [email protected] 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.
