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Hello Ton,
>How to calculate the degree of randomness. I want to be able to
>separate random from 'non' random time series and got stuck in the
>scientific background ..
The problem you raised is very difficult imho (there is a ton of
literature on the subject), and I would like to know a definite answer
: )
Anyway, something practical that can be done, and imho give a
reasonnable answer to your question, is to estimate the entropy rate
of the time series. The entropy rate of a dynamic process measures the
uncertainty that remains in the next information produced by the
process given complete knowledge of the past (and thus fully random
time series maximize the entropy rate). It is thus a natural measure
of the difficulty to predict the evolution of the process.
They are two main classes of entropy rates estimators: Lempel-Ziv
based algorithms and Context-Tree Weighting algorithms. The former are
simple to implement (a few lines of code), the latter usually a bit
better (i.e. need less data to be accurate) but much more involved.
I have made some experiments on NYSE US 100 stocks and it turned out
that all these stocks are highly unpredictable, some are even more
unpredictable (in the sense of the entropy rate) than the random
generator of the C library : )
Regards,
Nicolas
>
> Regards and thanks again, Ton.
>
>
> ----- Original Message -----
> From: vlanschot
> To: amibroker@xxxxxxxxxxxxxxx
> Sent: Monday, May 28, 2007 1:46 PM
> Subject: [amibroker] Corr Matrix via Gfx functions
>
>
> Thought I'd share the following code.
>
> PS
>
> //Simple application of the new Gfx functions, basically calculating
> //the correlation matrix of any WL of choice. You can easily adjust
> //this code to move to Var-Covar matrix, etc.
> // PS 28/05/07
>
> GfxSetOverlayMode(2); // Show Only Matrix
>
> function NrSecs(ListType,ListNr)
> {
> global NrPosPrices;
>
> if(ListType==1) ExtrList = CategoryGetSymbols
> (categoryGroup,ListNr);
> else if(ListType==2)ExtrList = CategoryGetSymbols
> (categoryWatchlist,ListNr);
> else if(ListType==3)ExtrList = CategoryGetSymbols
> (categoryIndustry,ListNr);
>
> NrSecurs=0;
> NrPosPrices=0;
>
> for( n=0; (Ticker=StrExtract( ExtrList, n))!= ""; n++)
> {
> NrSecurs=NrSecurs+1;
> SetForeign(Ticker);
> Prijs=C;
> RestorePriceArrays();
> NrPosPrices=NrPosPrices+IIf(Prijs!=Null AND
> Prijs>0,1,0);
> }
> return NrSecurs;
> }
>
> function PrintTxtInCell( Str, row, Col, CellWidth, CellHeight,
> HorzAdj, VertAdj, Formaat )
> {
> GfxDrawText( Str, Col * CellWidth + HorzAdj, row * CellHeight +
> VertAdj, (Col + 1 ) * CellWidth, (row + 1 ) * CellHeight, Formaat);
> }
>
> function PrintInCell( val, row, Col, CellWidth, CellHeight, HorzAdj,
> VertAdj )
> {
> GfxDrawText( NumToStr(val), Col * CellWidth + HorzAdj, row *
> CellHeight + VertAdj, (Col + 1 ) * CellWidth, (row + 1 ) *
> CellHeight, 1|32|4);
> }
>
> //CH = Param("CellH",20,10,100,5);
> //CW = Param("CellW",100,10,300,5);
> HA=0;
> VA=0;
>
> String = "" ;
> for ( x = 0 ; x < 200 ; x++ )
> {
> WList = CategoryGetName( categoryWatchlist, x );
> if (WList != "" )
> {
> String = String + WList +"," ;
> // Creates a list of WatchLists, NOT symbols !!!
> }
> }
> WatchList = ParamList ( "Watch List", String );
>
> WLnr=CategoryFind(WatchList,categoryWatchlist);
> WLSymbols = CategoryGetSymbols(categoryWatchlist,WLnr);
>
> NrSymbs = NrSecs(2,WLNr);
>
> CW= Status("pxwidth")/(NrSymbs+1);// In order to allow Rowheadings
> CH = Status("pxheight")/(NrSymbs+1);//Colheadings
>
> //GfxSetTextAlign(6 | 24);
>
> RetLB = Param("RetLB",1,1,100);
> CorrLB = Param("CorrLB",30,5,256);
>
> Start = BarCount-RetLB;
>
> ActBar = Min(BarCount-1,LastValue(SelectedValue(BarIndex())));
> ActD = LastValue(SelectedValue(DateTime()));
>
> GfxSelectFont( "MS Serif", CH/4,800);
> PrintTxtInCell( "CorrM @:\n"+NumToStr(ActD,formatDateTime), 0, 0,CW,
> CH, HA, VA, 1);
>
> for ( x = 0 ; (Ticker = StrExtract ( WLSymbols, x ))!="" ; x++ )
> {
> SetForeign(Ticker);
> RetTick = ROC(C,RetLB);
> FN = FullName();
> RestorePriceArrays();
>
> GfxSelectFont( "MS Serif", CH/4,800);
> PrintTxtInCell( Ticker, 0, x+1 ,CW, CH, HA, VA,1|32|4 );
>
> GfxSelectPen( colorBlue );
>
> for( i = 0; (Ticker2 = StrExtract ( WLSymbols, i))!="" ; i++ )
> {
> SetForeign(Ticker2);
> RetTick2 = ROC(C,RetLB);
> FN2 = FullName();
> RestorePriceArrays();
>
> if (Ticker2 == Ticker) Corr=1;
> else Corr = Correlation(RetTick, RetTick2, CorrLB);
>
> GfxSelectFont( "MS Serif", CH/4,800);
> PrintTxtInCell( Ticker2, i+1, 0, CW, CH, HA,
> VA,1|32|4);
> GfxSelectFont( "MS Serif", CH/4);
> Kleur = IIf(Corr[ActBar]>=0, colorGreen,colorRed);
> GfxSetTextColor(Kleur);
> PrintInCell( Corr[ ActBar ], i+1, x+1, CW, CH, HA,
> VA);
> //PrintInCell( Corr[ ActBar ] , i+1, x+1);
> GfxSetTextColor(colorBlack);
>
> GfxMoveTo( 0, (i+1) * CH);
> GfxLineTo( (x+2) * CW, (i+1) * CH );// Columns
> }
>
> GfxMoveTo( 0, (x+1)*CH); // Move to end of last column
> //GfxLineTo( 6 * CW, i * CH );
> }
>
> for( Col = 1; Col < NrSymbs+2; Col++ )
> {
> GfxMoveTo( Col * CW, 0);
> GfxLineTo( Col * CW, (NrSymbs+1) * CH );
> }
>
>
> Title="";
>
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