This indicator is a ported MQL5 indicator from http://www.mql5.com/ru/code/1748 (in Russian).
Formulas:
Range ratio = (MaxP-MinP)/sum, where
MaxP[i], MinP[i] - maximum and minimum prices for range from (i-Period+1) to i,
sum = sum of (High-Low) for range from (i-Period+1) to i.
Download:
The indicator was revised and updated