Polynomial and rational function modeling

In statistical modeling (especially process modeling), polynomial functions and rational functions are sometimes used as an empirical technique for curve fitting. == Polynomial function models == A polynomial function is one that has the form y = a n x n + a n − 1 x n − 1 + ⋯ + a 2 x 2 + a 1 x + a 0 {\displaystyle y=a_{n}x^{n}+a_{n-1}x^{n-1}+\cdots +a_{2}x^{2}+a_{1}x+a_{0}} where n is a non-negative integer that defines the degree of the polynomial.

Source: Wikipedia — Polynomial and rational function modeling (CC BY-SA 4.0)