Normalized Volume Oscillator

This volume indicator works best on comparatively small timeframes (15 minutes, for example).

Based on:
- Normalized Volume Oscillator - indicator for MetaTrader 4 <https://www.mql5.com/en/code/8208>
- Using Tick Volume in Forex: A Clear NVO Based Example <http://mechanicalforex.com/2010/08/using-tick-volume-in-forex-clear.html>

See also:
- Are price updates a good proxy for actual traded volume in FX? <https://www.fxstreet.com/education/are-price-updates-a-good-proxy-for-actual-traded-201104220000>