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G'Day Graham,
Thank you for your comprehensive reply. All the rules you have listed
seem logical as a statement. I learn by example so, I need to analyze
a few examples to gain a better understanding of looping functions.
I am trying to write a code which will detect first higher low trough
after a downtrend move which can be defined as two lower low troughs
and two lower low peaks. I am not sure if Zig function is best to do
that. Should I consider loops for this or use existing Zig function.
I could not locate anything in the library of similar nature so, I can
use is as an example of such a trend detection pattern.
Are you aware of any existing AFLs which addresses this or similar
pattern detection?
Kind Regards
Richard
--- In amibroker@xxxxxxxxxxxxxxx, Graham <kavemanperth@xxx> wrote:
>
> As a general rule I use loops when
>
> 1. Existing AB functions cannot fulfil requirements.
> eg use of AMA, Zig, Cum, or ApplyStop functions, or one of the
> many others available
>
> 2. The current bar value of a variable is calculated using the
> previous bar value of that same variable.
> eg EMA if that was not already a built in function in AB
>
> 3. The value of a variable is determined from a specific occurrence of
> a true condition, where that condition can have true values after that
> specific occurrence.
> eg trail stop value after Buy signal, that is not one of the
> existing ApplyStop function possibilities.
> This could be one that if could write simply would be
> HighestSince( Buy, H - ATR( 10 ) ), but this gets reset by any
> subsequent buy signals that you may not want to remove
> AB Applystop (ModePoint) currently has 2 possibilities if
> my memory is correct, they are
> A: Non-Volatile HighestSince( Buy, H ) - ValueWhen(
> buy, ATR( 10 ) ); and
> B: Volatile HighestSince( Buy, H ) - ATR( 10 );
> These bits of code would vary if you have a entry delay
after signal.
>
> 4. Loop through a set number series that have no direct relation to
> bar array identification as normally used in bar loops
> eg for( n=1; n<=5; n=n+2 )
>
> 5. Probably some others as well, but have written so many cannot
> always remember everything.
>
> Hopefully my examples of code above are correct, I just typed them
> into here from my poor memory
>
> --
> Cheers
> Graham Kav
> AFL Writing Service
> http://www.aflwriting.com
>
>
>
> 2009/2/20 richpach2 <richpach2@xxx>:
> > Hello,
> >
> > Can some please expain use of loop (if, while etc) expression in AFL?
> > When do one need to use a loop and when can one just rely on
> > processing of the array bar-by-bar. I am still learining AFL language
> > and this area is a bit grey.
> >
> > I noticed many Stop processing AFL use "for" loop but I don't
> > understand why.
> > Also, if I can use this statement toi define EMA;
> >
> > P = ParamField("Price field",-1);
> > Periods = Param("Periods", 15, 2, 300, 1, 10 );
> > Plot( EMA( P, Periods ), _DEFAULT_NAME(), ParamColor( "Color",
> > colorCycle ), ParamStyle("Style") );
> >
> > why would I try this AFL doc example;
> >
> > myema[ 0 ] = Close[ 0 ];
> > for( i = 1; i < BarCount; i++ )
> > {
> > myema[ i ] = 0.1 * Close[ i ] + 0.9 * myema[ i - 1 ];
> > }
> > This example iterates all bars of close array to calculate
> > exponential moving average.
> >
> > Regards
> > Richard
> >
> >
> >
> > ------------------------------------
> >
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>
------------------------------------
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