We have a similar filter in our library but we called it MovingAverage filter. In a sense, it is averaging the last N points.
Code:
/*
* MovingAverage of N points:
* MovingAverage = (MovingAverage*(N - 1) + CurrData)/N
* = MovingAverage*(N - 1)/N + CurrData/N
* = MovingAverage*(1 - Kf) + CurrData*Kf
* where 1/N = Kf
* (N - 1)/N = 1 - 1/N = 1 - Kf
*/