# Curvilinear Regression

Statistics Definitions > Curvilinear Regression Quadratic regression. BradBeattie|Wikimedia CommonsCurvilinear regression analysis fits curves to data instead of the straight lines you see in linear regression. Technically, it’s a catch all term for any regression that involves a curve. For example, quadratic regression and cubic regression. About the only type that isn’t includes in this catch-all definition is simple linear regression.

## Coordinates

Although Cartesian coordinate planes are drilled into us in school, the reality is very few real life events or data sets fit that neatly right-angled system. Coordinate systems are curvilinear if they are made from intersecting, curved surfaces. Comparison to Affine (bottom right) and Cartesian (bottom left) coordinates in two dimensional space. Image: Bbanerje|Wikimedia Commons.

The mathematics behind these beautiful coordinate systems are beyond the scope of this statistics site. However, you can find what I consider to be a clear description (mathematically speaking) of the system on James Foadi’s site.

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