you can use nls: see
?nls and its example. HTH. On 3/16/07, Hufkens Koen <[EMAIL PROTECTED]> wrote: > Hi list, > > I was wondering how I should go about fitting a sigmoid curve to a dataset. > More specifically how I estimate parameters a and b in the following > equation: > > 1 / 1+exp(-(x-a)*b) > > with b the steepness of the sigmoid curve and a the shift of the center of > the sigmoid curve relative to the center of your dataframe. The fit is in > function of x, the location within the input vector and y, an ecological > value. > > So I would like to estimate parameters a and b and a goodness of fit/ > F-value of some kind. > > Any suggestions? > > Kind regards, > Koen > > > -- > > Checked by AVG Free Edition. > > 11:27 > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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.
