Formulation on D41: Indicator function
F1735
Formulation 0
Let $X$ be a D11: Set.
The indicator function on $X$ with respect to $E \subseteq X$ is the D992: Function $$X \to \{ 0, 1 \}, \quad x \mapsto \begin{cases} 1, \quad & x \in E \\ 0, \quad & x \in X \setminus E \end{cases}$$
Subformulations
D382: Heaviside function

The Heaviside function is the D218: Basic boolean function $$\mathbb{R} \to \{ 0, 1 \}, \quad x \mapsto \begin{cases} 1, \quad & x \geq 0 \\ 0, \quad & x < 0 \end{cases}$$