exponential-moving-average | Calculate an exponential moving average from an array | Math library

I'm using Rx.Net and I have Observable that emits time series points (double, timestamp). Every time new point arrives I want to calculate average value from lets say last 30 seconds. I think I need some kind of overlapping Window/Buffer not based on count but timestamp.

I've found this topic with SlidingWindow implementation, but I cannot figure out how to fit this to my problem.

EDIT:

Thanks to this I learned that I can use Scan operator and buffer my points, so basicly this solves the problem. But maybe there is better way to do this?