This subsection will introduce two important values in linear algebra, namely the norm and determinant. Briefly, the norm gives length of a vector. The most commonly used norm is the *L ^{2}*-norm, which is also known as the Euclidean norm. Formally, the

*L*-norm of

^{p}*x*is calculated as follows:

The *L ^{0}*-norm is actually the cardinality of a vector. You can calculate it by just counting the total number of non-zero elements. For example, the vector

*A =[2,5,9,0]*contains three non-zero elements, therefore

*||A||*. The following code block shows the same norm calculation with numpy:

_{0}= 3In [24]: import numpy as np x = ...