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That being the case then why wouldn't Z =(A*B)+(C*Ref(Z,-1)); work without using loops? I guess that has been explored and there is more to the problem than I understand.
Barry
--- In amibroker@xxxxxxxxxxxxxxx, Thomas Ludwig <Thomas.Ludwig@xxx> wrote:
>
> Barry,
>
> PREV is NOT ref(c,-1) in this example but yesterday's value of Z. Otherwise
> PREV wouldn't be necessary im Metastock since MS has the same ref function
> like Amibroker.
>
> Regards,
>
> Thomas
>
> On 07.07.2009, 02:36:10 Barry Scarborough wrote:
> > If PREV works only on C in the example, wouldn't this run faster than using
> > a loop in AFL? Z =(A*B)+(C*Ref(C,-1)); Unless something has changed in the
> > latest AFL releases Tomasz's array processing is much faster than using
> > loops to perform the same function in AFL.
> >
> > Barry
> >
> > --- In amibroker@xxxxxxxxxxxxxxx, Thomas Ludwig <Thomas.Ludwig@> wrote:
> > > Hello,
> > >
> > > TJ once wrote:
> > >
> > > [quote]
> > > Hello,
> > >
> > > PREV in MS is needed because MS does NOT have looping.
> > >
> > > In AB, there are loop constructs so there is no need for PREV
> > > because loops give faster and more general way of solving coding
> > > problems.
> > >
> > > Since loops are more general they allow easy translation of every
> > > case where MS needs PREV.
> > >
> > > Statment like this:
> > > Z =(A*B)+(C*PREV);
> > >
> > > Using loop looks as follows:
> > >
> > > z = 0; // initialize
> > > for( i = 1; i < BarCount; i++ )
> > > {
> > > prev = Z[ i - 1 ]; // PREV is previous value of Z.
> > > Z[ i ] = A[ i ] * B[ i ] + C[ i ] * prev;
> > > }
> > >
> > > As you can see the statement is identical with the exception that
> > > AFL looping code uses [ ] operator to access individual array elements.
> > >
> > > Good thing is that AFL looping code is BarCount-times faster than MS
> > > code. Since 5 years of EOD data is 1300 bars, AFL looping code is 1300
> > > times faster than MS in that case.
> > >
> > > It is also possible to use AMA/AMA2 instead of PREV:
> > >
> > > Z = AMA2( A, B, C );
> > >
> > > which is shorter but AMA is less general than looping code.
> > > [/quote]
> > >
> > > HTH
> > >
> > > Greetings,
> > >
> > > Thomas
> > >
> > > On 15.06.2009, 13:06:00 Mubashar virk wrote:
> > > > Hi all,
> > > >
> > > > Has any one worked out a universal AFL Function = the perversity in
> > > > MetaStock that is called PREV.
> > > >
> > > > Thanks
> >
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>
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