// Downloaded From https://www.WiseStockTrader.com
_SECTION_BEGIN("fourier");
SetBarsRequired(100000,100000); 

Len = Param("FFT Length", 1024, 64, 10000, 10 ); 

Len = Min( Len, BarCount ); 

x = BarIndex(); 
x1 = x - BarCount + Len; 


input = C; 
a = LastValue( LinRegIntercept( input, Len - 1 ) ); 
b = LastValue( LinRegSlope( input, Len - 1 ) ); 


Lr = a + b * x1; 

data = input - Lr;// de-trending 

ffc = FFT(data,Len); 

for( i = 0; i < Len - 1; i = i + 2 ) 
{ 
   amp[ i ] = amp[ i + 1 ] = sqrt(ffc[ i ]^ 2  +  ffc[ i + 1 ]^2);   
   phase[ i ] = phase[ i + 1 ] = atan2( ffc[ i + 1], ffc[ i ] ); 
} 

auto = ParamToggle("Auto dominant cycle", "No|Yes", 1 ); 
sbar = Param( "Which FFT bin", 1, 0, 50 ); 

skipbin1 = ParamToggle("Skip 1st FFT bin", "No|Yes", 1 ); 

if( auto ) 
{ 
   sbar = int( LastValue(ValueWhen( amp == LastValue(Highest( IIf( skipbin1 AND x < 4, 0 , amp ) )), x / 2 )) ); 
} 

fv = Status("firstvisiblebar"); 

thisbar = Ref( int(x/2) == sbar, -fv); 
Plot( Ref(amp,-fv), 
"amplitude (bin " + Ref( int(x/2), -fv ) +")", IIf( thisbar, colorRed, colorBlack ),styleArea); 

Plot( IIf( BarCount - BarIndex() < Len, data, Null ) , 
"de-trended input ("+Len+" bars)", colorOrange, styleLeftAxisScale ); 
Plot( cos( phase[ sbar * 2 ] + (sbar) * x1 * 2 * 3.1415926 / Len ), 
" dominant cycle "+ Len/(sbar) + "(" + sbar + " bin) bars", colorBlue, styleOwnScale ); 

GraphZOrder=1; 
GraphXSpace = 10; 
_SECTION_END();