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I run into a function: $1_{[-n, n]^r}$. I guess this function equals 1 whenever x falls into $[-n, n]^r$. Am I right?

I met this function in an analysis paper which deals with measure and density of $L^p$ space.

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    $\begingroup$ Yes, and it is $0$ otherwise. $\endgroup$ Feb 7, 2014 at 23:11
  • $\begingroup$ @MichaelGreinecker That could be an answer. ;) $\endgroup$
    – apnorton
    Feb 7, 2014 at 23:19

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Yes, you're correct: It likely refers to an indicator function, also called a characteristic function. Other common notation is $\chi_A$, referring to the function that is $1$ for all $x \in A$, and $0$ for all $x \notin A$.

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