Polynomial Regression
Linear or not?
https://en.wikipedia.org/wiki/Linear_regression#/media/File:Polyreg_scheffe.svg
Example of a cubic polynomial regression, which is a type of linear regression. Although polynomial regression fits a nonlinear model to the data, as a statistical estimation problem it is linear, in the sense that the regression function E(y | x) is linear in the unknown parameters that are estimated from the data. For this reason, polynomial regression is considered to be a special case of multiple linear regression.
