Formulas:
Trend Force[i] = Up[i]-Dn[i], where
Up[i] = maximum (MaxPrice-ATR_Coeff*ATR) at range from (i-Period+1) to i,
Dn[i] = minimum (MinPrice+ATR_Coeff*ATR) at range from (i-Period+1) to i,
MaxPrice, MinPrice - maximum and minimum prices at range from (i-ATR_Period+1) to i,
ATR - Average True Range with ATR_Period.
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