Polynomial Fit Online Documentation

Polynomial fit

The relationship between the independent variable x and the dependent variable y is in the form of an nth degree polynomial of x.

Polynomial regression can so be categorized as follows for n from one to three:

1. Linear – if degree is 1. The equation of fit curve is:

$y = a + b \cdot x$

2. Quadratic – if degree is 2. The equation of fit curve is:

$y = a_2 \cdot x^2 + a_1 \cdot x + a_0$

3. Cubic – if degree is 3. The equation of fit curve is:

$y = a_3 \cdot x^3 + a_2 \cdot x^2 + a_1 \cdot x + a_0$

and so on. The order of polynomial can be generally n.

Fig. 2. Illustration of 4th order polynomial fit