I compared different techniques to get momentum of the series.
The 4 samples are:
1) Raw difference between price and price some bars ago
2) Built-in "change" function
3) Built-in "mom" function
4) Jedi's momentum - difference between current and previous multiplied by it's period
All results are identical.
So, we have two built-in functions that do the same thing: "change" and "mom". For brevity it is better to use "mom" when you need to get momentum of the series.