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 be categorized as follows for n from one to three:

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

   $$y = a + b \cdot x$$

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

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

3. Cubic – if degree is 3. The equation of the 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 the polynomial can generally be n.

Fig. 1. Illustration of 4th order polynomial fit