Could you provide the code that you're running, so we can see what you're trying to do? Even better would be a repeatable example.
Jeremy On 19 December 2012 09:42, Yann Labou <yann.la...@outlook.com> wrote: > Hey all, > > I'm trying to fit a non-linear model y ~ a * constant ^ b * x ^ c and > estimates the paramaters a, b and c. > > Using the nls function, I'm getting following error message: > > Error in nlsModel(formula, mf, start, wts) : > singular gradient matrix at initial parameter estimates > > If I logarithmize the whole equation log(y) ~ log (a) + b * log(constant) + > c * log(x) and fit the equation with lm, I get only NAs estimates for the > second term on the right side: > > Coefficients: (1 not defined because of singularities) > > Do you have any hints on how to fit this equation or any alternatives to > nls? > > Thanks, > Yann > > ______________________________________________ > 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. ______________________________________________ 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.
