Fitting parabolic function to data
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