[amibroker] Expanded Aroon Indicator

["Ken Close" <closeks@xxxxxxxx>]

I pulled the Aroon indicator, written by Tomasz, from the library.
While you can see it in its entirety there, let me reproduce one part of
it in order to ask my question.

Here is the indicator (one half of it), AroonUp:

H14 = HHV( High, 14 );

AroonUp =
100 * ( 14 - ( ( IIf(Ref(H ,-1) == H14 ,1 ,
	IIf(Ref(H ,-2 ) == H14 ,2,
	IIf(Ref(H ,-3 ) == H14 ,3, 
	IIf(Ref(H ,-4 ) == H14 ,4 ,
	IIf(Ref(H ,-5 ) == H14 ,5 ,
	IIf(Ref(H ,-6 ) == H14 ,6 ,
	IIf(Ref(H ,-7 ) == H14 ,7 ,
	IIf(Ref(H ,-8 ) == H14 ,8 , 
	IIf(Ref(H ,-9 ) == H14 ,9 ,
	IIf(Ref(H ,-10 ) == H14 ,10 ,
	IIf(Ref(H ,-11 ) == H14 ,11 ,
	IIf(Ref(H ,-12 ) == H14 ,12 ,
	IIf(Ref(H ,-13) == H14 ,13 ,
	IIf(Ref(H ,-14 ) == H14 ,14 ,0 ) ) ) ) ) )
) ) ) ) ) ) ) ) ) ) ) / 14;

Now, putting in a Parameter statement for the HHV length of 14 is
obviously meaningless because the ArronUp statement has 14 IIf
comparisons. 

My question for those loop writers who are more experienced than me is
this: how do you construct a loop structure which increase the
comparison sections as the lookback period increases or decreases the
comparison sections as the lookback period decreases.

Tomasz wrote this Aroon structure in the days (2001) before Amibroker
had loops and functions etc.  So how could it be written today in order
to easily change the lookback period without massive changes to the IIf
comparisons?

I hope the question is clear; if not, ask and I will attempt another
explanation.

Any ideas?

Thanks,

Ken

PS:  I have looked at this indicator before (outside of Amibroker) but
was stimulated by a recent article in the Ensign Newsletter that has
this to say about using the Aroon indicator.  BTW, a parameter screen
from the article showed a 6 period lookback which is what got me
thinking about how to change the AB Aroon indicator.

Ah, the text is too long to put in here.  Better, if you are interested,
is to go to the following address where you can read all of the Ensign
Newsletters, which sometimes contain useful info apart from the Ensign
program.

http://www.ensignsoftware.com/tips/newsletter.htm

The Aroon discussion is in the Sept Newsletter, the second section about
half way down the page.


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