Here is a quick telemetry lua script that I wrote for my NanoQX. I wanted to see what the average throttle setting that I was using during a flight. I use Timer2 to keep track of the time I have the throttle above -95. So every cycle of the script, I add the throttle value and track the number of times I have added the value so I can take the average.  You need to place this script in the following subdir on your SD card:

/SCRIPTS/{model_name}/

You can change the name from telem3.lua to any number from 0-6.

A couple of things to note, I use the timer2 and SA(UP) as my flag to average. SA(UP) is my throttle release. I also left the Count variable on the screen. It's how many times the throttle has been sampled. And the 00K counter is how many samples have been done in the ten thousands. I put this in since the Count variable wraps.