Polynomial Regression

Why polynomial regression?

Until now, we’ve assumed a linear relationship between features and targets. What if the assumption of linearity doesn’t hold even approximately? The figure below shows that the relationship between a single feature, $x$ and a single target, $y$ isn’t linear in the data set.

$$f(x) = \hat{y} = \sum_{i=0}^d w_i x^i$$ ...