ROC - Price change for Amibroker (AFL)

_SECTION_BEGIN("ROC");
P = ParamField( "Price field" );
periods = Param("Periods", 13, 1, 200, 1 );
Muaquamuc = Param("% Quamuc", 21, 1, 50, 1 );
Banquamuc = -Muaquamuc;
Plot( r=ROC( P, periods),"Price changes after "+ Periods + " is "+ _DEFAULT_NAME() + "%", ParamColor( "Color", colorCycle ), ParamStyle("Style")  );
PlotOHLC( r,r,0,r, "", IIf( r > 0, colorRed, colorGreen ), styleCloud | styleClipMinMax, Banquamuc, Muaquamuc ); 
Plot(21,"",colorRed,styleLine);
Plot(0,"",colorBlack,styleLine);
Plot(-21,"",colorBlue,styleLine);
Buy = Cross(r,Banquamuc);
Sell = Cross(Muaquamuc,r);

Filter=Buy OR Sell;
Buy=ExRem(Buy,Sell); Sell=ExRem(Sell,Buy); 
AddColumn(Close,"Close");AddColumn(Volume,"Volume");AddColumn(r,"ROC(13)");AddColumn(Buy,"Buy"); AddColumn(Sell,"sell"); 

_SECTION_END();