“signum function”的概念、定义、翻译、参考文献-科学参考

单词	signum function
释义	signum function Mathematics The real function, denoted by sgn, defined by $sgn x = {\begin{matrix} - 1, & if x < 0, \\ 0, & if x = 0, \\ 1, & if x > 0. \end{matrix}$ The name and notation come from the fact that the value of the function depends on the sign of x. This notation is also used for the parity of permutations, that is, $sgn σ = {\begin{matrix} \begin{matrix} 1 & if \end{matrix} σ is even, \\ \begin{matrix} - 1 & if σ is odd . \end{matrix} \end{matrix}$
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