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Re: [amibroker] MetaStock's PREV



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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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