Re: [amibroker] MetaStock's PREV
This is an excellent explanation and very example.
Thank you very much.
--
From: "Thomas Ludwig"
Sent: Tuesday, June 16, 2009 7:00 PM
To:
Subject: Re: [amibroker] MetaStock's PREV
> 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
>
>
>
>
> IMPORTANT PLEASE READ
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>
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>
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>
> For NEW RELEASE ANNOUNCEMENTS and other news always check DEVLOG:
> http://www.amibroker.com/devlog/
>
> Yahoo! Groups Links
>
>
>
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Re: [amibroker] MetaStock's PREV
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
IMPORTANT PLEASE READ
This group is for the discussion between users only.
This is *NOT* technical support channel.
TO GET TECHNICAL SUPPORT send an e-mail directly to
SUPPORT {at} amibroker.com
TO SUBMIT SUGGESTIONS please use FEEDBACK CENTER at
http://www.amibroker.com/feedback/
(submissions sent via other channels won't be considered)
For NEW RELEASE ANNOUNCEMENTS and other news always check DEVLOG:
http://www.amibroker.com/devlog/
Yahoo! Groups Links
<*> To visit your group on the web, go to:
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<*> Your email settings:
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Re: [amibroker] MetaStock's PREV
Thanks, TJ. I will look into the archives. From: Tomasz Janeczko Sent: Monday, June 15, 2009 3:43 PM To: amibroker@yahoogroups.com Subject: Re: [amibroker] MetaStock's PREV No, because it is sick idea implemented in MS because they don't have a normal loop construct in the language. Metastock PREV essentially re-calculates entire array (number of bars)-times resulting (number of bars) performance degradation. So if you have say 1 bars, the code runs 1 slower. Everything that you do in MS using PREV should be coded using the loop in first place instead - and the resulting code will be 2 or 4 orders of magnitude faster. Search the archive of the mailing list how to write loop equivalent. Best regards, Tomasz Janeczko amibroker.com - Original Message - From: Mubashar virk To: amibroker@yahoogroups.com Sent: Monday, June 15, 2009 1:06 PM Subject: [amibroker] MetaStock's PREV Hi all, Has any one worked out a universal AFL Function = the perversity in MetaStock that is called PREV. Thanks
Re: [amibroker] MetaStock's PREV
No, because it is sick idea implemented in MS because they don't have a normal loop construct in the language. Metastock PREV essentially re-calculates entire array (number of bars)-times resulting (number of bars) performance degradation. So if you have say 1 bars, the code runs 1 slower. Everything that you do in MS using PREV should be coded using the loop in first place instead - and the resulting code will be 2 or 4 orders of magnitude faster. Search the archive of the mailing list how to write loop equivalent. Best regards, Tomasz Janeczko amibroker.com - Original Message - From: Mubashar virk To: amibroker@yahoogroups.com Sent: Monday, June 15, 2009 1:06 PM Subject: [amibroker] MetaStock's PREV Hi all, Has any one worked out a universal AFL Function = the perversity in MetaStock that is called PREV. Thanks
