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What do the curly brackets mean in this context?

$f(x) = 2 \cdot x \cdot 1_{x>0}$

Is this a condition?

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    @Soo : Since your title mentions "sub curly brackets", I wonder if you meant 2\cdot x\cdot1_{\{x>0\}}?2012-02-14

1 Answers 1

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The $\Bbb 1_{x>0}$ is the indicator function $^1$ that indicates if $x$ is greater than $0$ or not. $1_{x>0}=\begin{cases} 1, ~~x>0\\0, ~~x \le 0\end{cases}$

This makes your function into,

$f(x)=\begin{cases}2x,~~x>0\\0, ~~x \le0 \end{cases}$

Footnotes:

$^1$(also called the Characteristic function, denoted by $\chi_A$ is the function that takes $1$ when $x \in A$ and $0$ otherwise.)

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    Macaulay brackets anybody?2018-08-15