Hello, I'd like to fit a logit function to my data. The data is distributed like a logit (like in this plot on wikipedia http://en.wikipedia.org/wiki/File:Logit.png) but the values on the x-axis are not between 0 and 1. I don't think using a glm is the solution because I simply want to infer the parameters of the logit function (offset, compression, slope...), so I can apply it to all my values on x and get my value y. It works in gnuplot with this command: fit f(x) 'myData' using x:y via a,b,c,d and after some iterations gnuplot will return the values a,b,c,d.... Is there something like this in R? Thanks for the help! Sylvia [[alternative HTML version deleted]]
On Mon, Feb 21, 2011 at 12:13:09PM +0100, Sylvia Tippmann wrote:> Hello, > > I'd like to fit a logit function to my data. > The data is distributed like a logit (like in this plot on wikipedia http://en.wikipedia.org/wiki/File:Logit.png) > but the values on the x-axis are not between 0 and 1. > I don't think using a glm is the solution because I simply want to > infer the parameters of the logit function > (offset, compression, slope...), so I can apply it to all my values on > x and get my value y.Two ideas: 1) scale your data so it does fit in [0,1] before fitting a glm 2) Use nls() to fit whatever function you find suitable cu Philipp -- Dr. Philipp Pagel Lehrstuhl f?r Genomorientierte Bioinformatik Technische Universit?t M?nchen Wissenschaftszentrum Weihenstephan Maximus-von-Imhof-Forum 3 85354 Freising, Germany http://webclu.bio.wzw.tum.de/~pagel/