L0 Norm

linear-algebra

Definition

$L_0$ Norm

Let $v\in F^d$ be a $d$-dimensional vector over a field $F$. The $L_0$ “norm” (mathematically it’s not a norm, but a cardinality measure) is the number of non-zero components:

$$||v|{|}_0=|\{1\le i\le d\mid v_i\ne 0\}$$