How to do a Multivariable Polynomial Fit with a known Structure

I have a bunch of data I would like to fit with a polynomial in order to model the current to force curve of a reluctance actuator. For simplicity I want the following structure: F(i,gap) = A*i^2 / (gap + B)^2. I was trying to use the polyfitn function, but I cannot seem to get it to work with the constant term dependence in the denominator. Any suggestions on how to do a least squares fit for this structure of polynomial?

Nick

Answer 1

[Shashank Prasanna]

Without using any of the toolboxes you can fit custom equations following the steps

http://www.mathworks.com/help/matlab/math/example-curve-fitting-via-optimization.html