// 2020.7.30 version
// This indicator is for the second filter in Triple Screen Trading System
// force index will combine volume and price together to decide the power of price change
// force index = volume * (Change of Price)
// try to smooth the series of force index by ema force index
// Method to use this index
// This indicator is for the second filter in Triple Screen Trading System
// if Trend is bull, long when force index is below 0
// if Trend is bear, short when force index is above 0
// As for how to decide bullish market or bearish market, please check it according to the first filter of Triple Screen Trading System