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Why are we Stacking these Variables?


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Why are we Stacking these Variables?

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  #1 (permalink)
Dallas, TX
 
Experience: Intermediate
Platform: ToS, TradeGuider, eSignal, AmiBroker
Broker: TD Ameritrade/eSignal
Trading: Stocks
 
DonStar's Avatar
 
Posts: 68 since Dec 2011
Thanks: 28 given, 41 received

Hi ALL: I have a piece of code written in AmiBroker AFL that I am trying to unserstand.

 
Code
xBarIndex= BarIndex();
x= xBarIndex;
xLastValue= LastValue( x );
This is the output I get from the debug window:
Last value of x = 520
Bar Index = 511

Okay, 520 is the last bar of data. No matter which bar I select the LastValue is always 520. BarIndex in this example is 511, but it changes to a different number when I select a different bar.

So my question is: why put BarIndex() into the variable (xBarIndex)?

And then why put xBarIndex into another variable (x)?

And finally, whay use x to compute LastValue? Why not just do this:
xLastValue( BarIndex() )

I'm sure there is a reason behind this and I would like to understand the logic.

Can anyone help me understand this?

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  #2 (permalink)
Asheville, North Carolina
 
 
Posts: 24 since Sep 2010
Thanks: 1 given, 15 received

You are dealing with poorly written code. BarIndex() returns an array in which the first bar is 0 in contrast to Barcount which is the number of bars (a single number) starting at 1. If this makes no sense, read the section of the Users Guide regarding arrays. So for the last bar BarIndex() = BarCount - 1.

All you need is one line: xBarIndex = LastValue(BarInddex();

You should read the Help and Users Guide for a full description of both and also look at the "Common Errors" section which discusses common errors using them.

In addition to reading Help and User Guide, put this little piece of code in a blank window and it will help you understand the difference as you click on different bars.

xBarIndex= BarIndex();
x= xBarIndex;
xLastValue= LastValue(BarIndex());//LastValue( x );
Title = "xbarindex=" + xbarindex + " x=" + x + " xlastvalue=" + LastValue(x) + " barcount = " + BarCount;

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January 25, 2012


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