How to say "it's a function of ..." in Chinese?
In daily conversations, we do not use "甲是乙的函数", instead, we do use "甲取決於乙" for something that we think is crucial.

在日常口語中，的確不常使用"甲是乙的函数"這種用法，可以考慮使用"甲取決於乙"這種翻法來表達某個關鍵因素。

Translation of the sentence said by the former Bulls coach Phil Jackson:


  肯定是教練... 你的精力取決於你做什麼。當教練時，你是透過腦力參與比賽。