// Automatic Linear Trend Channel 
// Trend is defined using an example trend: MA(cp,100)
// Amibroker AFL code by Edward Pottasch, November 2011 

_SECTION_BEGIN("parameters");
sdfact=Param("Standard Deviation Factor",2,0.5,5,0.1); 
offset=Param("Offset",2,1,50,1); 
tc=ParamList("Channel Display",List="No Channel|Channel|ChannelRT|Both Channels",1);
_SECTION_END();

function getUptrend(cp)
{
	return IIf(cp>MA(cp,100),1,0);
}
function getDowntrend(cp)
{
	return IIf(cp<=MA(cp,100),-1,0);
}

// trend definition
cp=(H+L)/2;
TrendUp=getUptrend(cp);
TrendDown=getDowntrend(cp);
totalTrend=IIf(TrendUp,TrendUp,TrendDown);
dtotalTrend=totalTrend-Ref(totalTrend,-1);
vtotalTrend=ValueWhen(dtotalTrend,dtotalTrend);

// definition start points up and down trend
cbull=vtotalTrend>0 AND Ref(vtotalTrend,-1)<0;cbull=Ref(cbull,1);
cbear=vtotalTrend<0 AND Ref(vtotalTrend,-1)>0;cbear=Ref(cbear,1);
cbull=vtotalTrend>0 AND Ref(vtotalTrend,-1)<0;cbull=Ref(cbull,1);cbull[BarCount-1]=1;
cbear=vtotalTrend<0 AND Ref(vtotalTrend,-1)>0;cbear=Ref(cbear,1);cbear[BarCount-1]=1;

// definition areas up and down trend
nwbull=Ref(Flip(cbull,cbear),-1);nwbear=Ref(Flip(cbear,cbull),-1);

xxbull=BarsSince(cbull);xxbull[BarCount-1]=xxbull[BarCount-2]+1;
aaabull=LinRegIntercept(cp,xxbull);bbbbull=LinRegSlope(cp,xxbull);
daabull=Ref(ValueWhen(cbear,aaabull,0),-1);dbbbull=Ref(ValueWhen(cbear,bbbbull,0),-1);
yybull=daabull+dbbbull*(xxbull-1);yybull=IIf(xxbull>Max(offset,1),yybull,Null);
wdbull=sdfact*StdErr(cp,xxbull);wdbull=Ref(ValueWhen(cbear,wdbull,0),-1);

xxbear=BarsSince(cbear);xxbear[BarCount-1]=xxbear[BarCount-2]+1;
aaabear=LinRegIntercept(cp,xxbear);bbbbear=LinRegSlope(cp,xxbear);
daabear=Ref(ValueWhen(cbull,aaabear,0),-1);dbbbear=Ref(ValueWhen(cbull,bbbbear,0),-1);
yybear=daabear+dbbbear*(xxbear-1);yybear=IIf(xxbear>Max(offset,1),yybear,Null);
wdbear=sdfact*StdErr(cp,xxbear);wdbear=Ref(ValueWhen(cbull,wdbear,0),-1);

llbull=LinearReg(cp,xxbull);llbull=IIf(xxbull>Max(Offset,1),llbull,Null);
llbullp=LinearReg(cp,xxbull)+sdfact*StdErr(cp,xxbull);llbullp=IIf(xxbull>Max(Offset,2),llbullp,Null);
llbullm=LinearReg(cp,xxbull)-sdfact*StdErr(cp,xxbull);llbullm=IIf(xxbull>Max(Offset,2),llbullm,Null);
llbear=LinearReg(cp,xxbear);llbear=IIf(xxbear>Max(Offset,1),llbear,Null);
llbearp=LinearReg(cp,xxbear)+sdfact*StdErr(cp,xxbear);llbearp=IIf(xxbear>Max(Offset,2),llbearp,Null);
llbearm=LinearReg(cp,xxbear)-sdfact*StdErr(cp,xxbear);llbearm=IIf(xxbear>Max(Offset,2),llbearm,Null);

_SECTION_BEGIN("Chart Colors");
SetChartBkColor(ParamColor("Background Color",colorBlack));
SetChartOptions(0,chartShowDates);
SetBarFillColor(IIf(C>O,ParamColor("Candle UP Color",colorGreen),IIf(C<=O,ParamColor("Candle Down Color",colorRed),colorLightGrey)));
Plot(C,"Price",IIf(C>O,ParamColor("Wick UP Color",colorDarkGreen),IIf(C<=O,ParamColor("Wick Down Color",colorDarkRed),colorLightGrey)),64,0,0,0,0);

switch(tc)
{
case("No Channel"):
break;
case("Channel"):
Plot(IIf(nwbull,yybull,Null),"",bbb=ColorRGB(0,255,0),styleDashed);
Plot(IIf(nwbull,yybull+wdbull,Null),"",bbb,styleThick);
Plot(IIf(nwbull,yybull-wdbull,Null),"",bbb,styleThick);
Plot(IIf(nwbear,yybear,Null),"",sss=ColorRGB(255,0,0),styleDashed);
Plot(IIf(nwbear,yybear+wdbear,Null),"",sss,styleThick);
Plot(IIf(nwbear,yybear-wdbear,Null),"",sss,styleThick);
PlotOHLC(IIf(nwbull,yybull+wdbull,Null),IIf(nwbull,yybull+wdbull,Null),IIf(nwbull,yybull-wdbull,Null),
IIf(nwbull,yybull-wdbull,Null),"",ColorRGB(10,15,10),styleCloud|styleNoLabel,0,0,0,-1); 
PlotOHLC(IIf(nwbear,yybear+wdbear,Null),IIf(nwbear,yybear+wdbear,Null),IIf(nwbear,yybear-wdbear,Null),
IIf(nwbear,yybear-wdbear,Null),"",ColorRGB(15,10,10),styleCloud|styleNoLabel,0,0,0,-1); 
break;
case("ChannelRT"):
Plot(IIf(nwbull,llbull,Null),"",colorGreen,styleDashed,0,1,0,1);
Plot(IIf(nwbull,llbullp,Null),"",colorGreen,styleDashed,0,1,0,1);
Plot(IIf(nwbull,llbullm,Null),"",colorGreen,styleDashed,0,1,0,1);
Plot(IIf(nwbear,llbear,Null),"",colorRed,styleDashed,0,1,0,1);
Plot(IIf(nwbear,llbearp,Null),"",colorRed,styleDashed,0,1,0,1);
Plot(IIf(nwbear,llbearm,Null),"",colorRed,styleDashed,0,1,0,1);
PlotOHLC(IIf(nwbull,llbullp,Null),IIf(nwbull,llbullp,Null),IIf(nwbull,llbullm,Null),
IIf(nwbull,llbullm,Null),"",ColorRGB(10,15,10),styleCloud|styleNoLabel,0,0,0,-1); 
PlotOHLC(IIf(nwbear,llbearp,Null),IIf(nwbear,llbearp,Null),IIf(nwbear,llbearm,Null),
IIf(nwbear,llbearm,Null),"",ColorRGB(15,10,10),styleCloud|styleNoLabel,0,0,0,-1); 
break;
case("Both Channels"):
Plot(IIf(nwbull,yybull,Null),"",bbb=ColorRGB(0,255,0),styleLine);
Plot(IIf(nwbull,yybull+wdbull,Null),"",bbb,styleThick);
Plot(IIf(nwbull,yybull-wdbull,Null),"",bbb,styleThick);
Plot(IIf(nwbear,yybear,Null),"",sss=ColorRGB(255,0,0),styleLine);
Plot(IIf(nwbear,yybear+wdbear,Null),"",sss,styleThick);
Plot(IIf(nwbear,yybear-wdbear,Null),"",sss,styleThick);
Plot(IIf(nwbull,llbull,Null),"",colorGreen,styleDashed,0,1,0,1);
Plot(IIf(nwbull,llbullp,Null),"",colorGreen,styleDashed,0,1,0,1);
Plot(IIf(nwbull,llbullm,Null),"",colorGreen,styleDashed,0,1,0,1);
Plot(IIf(nwbear,llbear,Null),"",colorRed,styleDashed,0,1,0,1);
Plot(IIf(nwbear,llbearp,Null),"",colorRed,styleDashed,0,1,0,1);
Plot(IIf(nwbear,llbearm,Null),"",colorRed,styleDashed,0,1,0,1);
break;
}
_SECTION_END();