Thank you very much, Jun. This is what I was looking for. Best!
Dani On Wed, 2009-08-19 at 09:52 -0500, Jun Shen wrote: > I would suggest a model with a baseline level, something like > > nls(AMP~E0+(Emax-E0)*Time**gamma/(EC50**gamma+Time**gamma),data=your > data, > start=list(EC50=50,gamma=2,E0=0.2,Emax=1.2))->mod.test > > AIC(mod.test) does improve. Hope this helps. > > Jun > > On Wed, Aug 19, 2009 at 5:04 AM, Dani Valverde > <[email protected]> wrote: > Hello, > I have this data: > Time AMP > 0 0.2000000 > 10 0.1958350 > 20 0.2914560 > 40 0.6763628 > 60 0.8494534 > 90 0.9874526 > 120 1.0477692 > > where AMP is the concentration of this metabolite with time. > If you plot > the data, you can see that it could be fitted using a logistic > regression. For this purpose, I used this code: > > AMP.nls <- nls(AMP~SSlogis(Time,Asym, xmid, scal), data = > concentrations,model=T) > > When plotting the fitted function, it seems that it fits quite > well at > the end of the time. However, at the beginning it seems that > the fit is > not so good. How can I achieve a better fit? Forgive me if it > is a > stupid question, but I am just starting with non linear > regression. > Thank you, > > Dani > -- > [?] > > ______________________________________________ > [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. > > > > -- > Jun Shen PhD > PK/PD Scientist > BioPharma Services > Millipore Corporation > 15 Research Park Dr. > St Charles, MO 63304 > Direct: 636-720-1589 > -- Daniel Valverde Saubí Grup de Biologia Molecular de Llevats Facultat de Veterinària de la Universitat Autònoma de Barcelona Edifici V, Campus UAB 08193 Cerdanyola del Vallès- SPAIN Tlf. +34 93 581 1910 Fax: +34 93 581 1573 ______________________________________________ [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.
