I have a math equation that has II in it I cannot understand what the II function is and what it does. I really appreciate it if you can explain what it is.
1 Answer
$\begingroup$It is a Capital i, as "indicator function"
you can also find $\mathbb{1}$ and indicates that the function is 1 for the values in the braces and zero elsewhere
Example,
Suppose you have the following function
$$ y = \begin{cases} x, & \text{if $0<x<1$ } \\ 2-x, & \text{if $1\leq x\leq 2$}\\ 0, & \text{elsewhere} \end{cases}$$
you can compact the notation and write
$$y=\{1-|1-x|\}\cdot\mathbb{1}_{[0;2]}(x)$$
$\endgroup$
