Bollinger Band Top Bottom Detector - Amibroker AFL Code

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_SECTION_BEGIN("Price");

SetChartOptions(0,chartShowArrows|chartShowDates);
_N(Title = StrFormat("{{NAME}} - {{INTERVAL}} {{DATE}} Open %g, Hi %g, Lo
%g, Close %g (%.1f%%) {{VALUES}}", O, H, L, C, SelectedValue( ROC( C, 1 ) )
));
Plot( C, "Close", ParamColor("Color", colorBlack ), styleNoTitle |
ParamStyle("Style") | GetPriceStyle() ); 
_SECTION_END();
 
_SECTION_BEGIN("Colored Bollinger Bands");
pr=Param( "Period",20,0,100,1);
P = ParamField("Price field",-1);
Style = ParamStyle("Style") | styleNoRescale | styleNoLabel |styleDashed;
BBT=BBandTop(P,pr,2);
BBB=BBandBot(P,pr,2);
topcond = (Cross(BBT,C)OR C>BBT)AND Ref(C, -1)> BBT;
botcond = ( Cross(C,BBB))AND Ref(C, -1 < BBB);
bbtcolor = IIf( BBT> Ref (BBT, -1), colorDarkGreen,colorRed );
bbbcolor = IIf( BBB > Ref (BBB, -1), colorDarkGreen,colorRed );
Plot( BBT, "BBTop" + _PARAM_VALUES(), bbtcolor, styleLine|styleThick); 
Plot( BBB, "BBBot" + _PARAM_VALUES(), bbbcolor, styleLine|styleThick ); 
PlotOHLC( BBT,BBT,BBB,BBB, "", ParamColor("Color",colorRose),styleCloud );
Buy=botcond;
Sell=topcond ;
// If you feel there are too many arrows you can un-comment the next twolines.
//Buy=ExRem(Buy,Sell);
//Sell=ExRem(Sell,Buy);
PlotShapes(shapeUpArrow * Buy, colorGreen, 0, L, - 10);
PlotShapes(shapeDownArrow * Sell, colorRed, 0, H, - 10);
 _SECTION_END();