Degree of polynomial surface fitting (cftool - fit)

Good morning,

I need to fit a surface from a set of experimental points using a polynomial model. Curve fitting toolbox (cftool) allows to perform it and to obtain polynomial coefficients up to fifth degree for x and y. The fitted surface is not enough accurate and I would like to increase the polynomial degree.

How can I increase the polynomial degree of the surface?

Thank you!

Answer 1

[Rishabh Mishra]

Hi,

You can use the ‘polyfitn’ toolbox to serve your required purpose. The ‘polyfitn()’ function is able to accurately predict the coefficients of higher degree (degree > 5) polynomials given the ‘x’ & ‘y’ values.

The general syntax for the function is:

% define the degree of polynomial
deg = 8 
fit = polyfitn(x,y,deg)

‘fit.Coefficients’ stores the coefficient values of the polynomial.

Hope This helps.