// Downloaded From https://www.WiseStockTrader.com
Periods = Param ("Time periods",10,1,350,1);

er = (abs(C - Ref(C,-Periods))) /(Sum(abs(C-Ref(C,-1)),Periods));

Plot( er, _DEFAULT_NAME(), ParamColor( "Color", colorCycle ), ParamStyle("Style")  );
Buy = Cross(er,.5);
Sell =Cross(.5,er)  ;