Hi Duncan, Thanks for your reply. You saved my Day :)
Thanks, Henri On Thu, Oct 6, 2011 at 12:07 PM, Duncan Murdoch <murdoch.dun...@gmail.com> wrote: > On 11-10-06 4:59 AM, Henri Mone wrote: >> >> Dear R users and experts, >> >> I want to fit a shifted parabolic function with the following >> functional form to my data: >> >> f(x)=a0*(x+a1)^2+a2 >> >> (a0, a1 and a2 are scaling factors.) >> What is standard approach to do this in R? I tried the "lm" function >> in R but I got problems getting the above functional form. >> >> Any help is welcome :) . > > That can be expanded into a regular quadratic: > > (a0*a1^2 + a2) + 2*a0*a1*x + a0*x^2 > > So fit a regular quadratic, and then solve for a0, a1, a2 from the resulting > coefficients. The only tricky bit will be computing errors on the a's. > > Duncan Murdoch > ______________________________________________ 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.
