polynomial is badly conditioned

Hi guys,

I'm trying to obtain a fitted formula for a dataset, so I used basic fitting. Below is the original data.

Using basic fitting, I chose a 5th degree polynomial. However, matlab gives me the warning "Polynomial is badly conditioned"

It seems like a perfect fit to me, so is it save to ignore this warning? Lower degree polynomials won't fit as good as this one and keep giving me the same warning (except a 2 degree, which is too low).

Or any other advise?

Answer 1

[Harsha Priya Daggubati]

Hi,

Warning messages result if N is >= length(X) [N is the order of polynomial], if X has repeated, or nearly repeated, points, or if X might need centering and scaling. Try modifying your input data.

Hope this helps!