# continuation of the “n-th derivative” function [closed]

let $D_{\mathbb N}$ be the standard "n-th derivative" function

is it possible to make a continuation of $D_{\mathbb N}$ to non integer values?

i mean a function $D_{\mathbb R}$ such that $D_{\mathbb R}(x,f)=D_{\mathbb N}(n,f)$ for all $x=n\in\mathbb N$

it should be something relevant, linear interpolation usually doesn't make any sense.

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## closed as no longer relevant by Qfwfq, Bill Johnson, Ryan Budney, Andres Caicedo, Andy PutmanJan 23 '12 at 3:20

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