For today I’d like to bring back attention to something from my original, summer 2015, A to Z. The characteristic function is a way of picking out sets of things. Like, there’s a characteristic function that picks out “all the real numbers between 2 and 4”. Or “all the prime integers”. Or “all the space within a set distance of this point”. It’s a handy tool for breaking up a problem into several smaller problems, without requiring that we write it out as more problems. We can use the tools for regular functions to deal with complicated and weird cases.
There are several things called characteristic functions. The other really important one turns up in probability, and the essay linked there isn’t about that one.
Other Summer 2015 A to Z essays are at this link. Also I learn I didn’t tag these essays the way I would come to later on. I’ll have to fix that sometime.
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