Norm (math)

• https://en.wikipedia.org/wiki/Norm_(mathematics)

a norm is a function from a real or complex vector space to the non-negative real numbers that behaves in certain ways like the distance from the origin: it commutes with scaling, obeys a form of the triangle inequality, and is zero only at the origin.

p-norm

$$\|\mathbf{x}\|_p := \left(\sum_{i=1}^n \left|x_i\right|^p\right)^{1/p}.$$

2-norm is the Euclidean norm.

Unit circle and regularization

Lasso (statistics)