Re: [amibroker] Re: Need Help With FirstVisibleBarIndex

Fri, 01 Sep 2006 13:15:39 -0700

They are both zero based but BarIndex() returns the array from 0 to "firstvisiblebarindex" (or "lastvisibilebarindex").  BarCount is the number of things in the array which is the same number for "firstvisiblebarindex" and "firstvisiblebarcount".  Look up discussion of array vs. number.
 
Bill
 
======================================

There is a fundamental difference between BarCount and BarIndex(). BarCount is a numeric variable that holds just one number (the count of elements in array). On the other hand BarIndex() is a function that returns ARRAY representing consecutive index of each bar.

======================================

BarCount constant gives the number of bars in array (such as Close, High, Low, Open, Volume, etc). Array elements are numbered from 0 (zero) to BarCount-1.

===================================

SYNTAX BarIndex()
RETURNS ARRAY
FUNCTION
returns zero-based bar number - the same as Cum(1)-1 but it is much faster than Cum(1) when used in Indicators
 
========================
 
 
 
----- Original Message -----
From: "wlandry01" <[EMAIL PROTECTED]>
To: <amibroker@yahoogroups.com>
Sent: Friday, September 01, 2006 3:18 PM
Subject: [amibroker] Re: Need Help With FirstVisibleBarIndex

>
> Bill,
>
> Sorry, but I meant to ask in my response to your note
> why "FirstVisibleBar" and "FirstVisibleBarIndex" would
> return the same values.  According to the AFL Reference,
> one is the bar number and one is the bar index.  I thought
> those differ by one.
>
> Thanks,
>
>
> Wayne
>
>
>
> --- In amibroker@yahoogroups.com, "wavemechanic" <[EMAIL PROTECTED]> wrote:
>>
>> Put SetBarsRequired(10000,0) at the beginning of the code (overrides
> QuickAFL) and both sets will return the same values.  Note, if blank
> right bars are visible they are counted.  However, for your
> application of finding highest C, etc. look at the code and charts
> that I posted before and you will see that it is not needed in that
> case because the blank bars do not change the highest C, etc.  Read
> about QuickAFL and turn on the chart timing display (Tools >
> Preferences > Display Timing).  Play with this stuff and all will
> become crystal clear - sort of.
>>
>> Bill
>>
>>
>> ----- Original Message -----
>> From: "wlandry01" <[EMAIL PROTECTED]>
>> To: <amibroker@yahoogroups.com>
>> Sent: Friday, September 01, 2006 11:59 AM
>> Subject: [amibroker] Re: Need Help With FirstVisibleBarIndex
>>
>>
>> >
>> > Graham,
>> >
>> > According to the AFL Reference, "FirstVisibleBar" returns the bar
>> > number while "FirstVisibleBarIndex" returns the bar index.
>> >
>> > With respect to Fred's comments, the AFL Reference indicates that both
>> > are available in Indicator mode only, so checking them in Exploration
>> > mode is not an option.  That's consistent with my experience.
>> >
>> > I copied Fred's code and displayed it on a chart and I find that the
>> > "FirstVisibleBar" and "LastVisibleBar" indicators give me non-zero
>> > values that do not change as I change the chart time frame.  The
>> > numbers don't appear to correspond to anything on the chart.  That
>> > part I don't understand. 
>> >
>> > The "FirstVisibleBarIndex" and "LastVisibleBarIndex" give the index
>> > numbers and they do change with the chart.  That part is consistent
>> > with the AFL Reference.  I'm not familiar with the use of _Trace so I
>> > don't know how to use that to check on this question.
>> >
>> > If would be helpful if someone could advise as to what the
>> > "FirstVisibleBar" and "LastVisibleBar" indicators are showing in the
>> > code that Fred provided (see below).
>> >
>> > Thanks,
>> >
>> >
>> > Wayne
>> >
>> >
>> >
>> >
>> >
>> > Wayne
>> >
>> >
>> >
>> >
>> > --- In amibroker@yahoogroups.com, Graham <kavemanperth@> wrote:
>> >>
>> >> Thanks Fred. So FirstVisibleBar delivers the barindex() value as well
>> >> FirstVisibleBarIndex. I would have thought that they would be
> different
>> >> otherwise why have the both of them
>> >> That is gong to require reworking of all existing AFL that use
>> >> FirstVisibleBar as a 0 or 1 value
>> >>
>> >>
>> >> --
>> >> Cheers
>> >> Graham
>> >> AB-Write >< Professional AFL Writing Service
>> >> Yes, I write AFL code to your requirements
>> >> http://e-wire.net.au/~eb_kavan/ab_write.htm
>> >>
>> >> On 01/09/06, Fred <ftonetti@> wrote:
>> >> >
>> >> > Apparently ? Appears to ?
>> >> >
>> >> > When in doubt use Explore or Plot or _Trace ...
>> >> >
>> >> > Plot(Status("FirstVisibleBar"), "FVB", colorWhite);
>> >> > Plot(Status("FirstVisibleBarIndex"), "FVBI", colorYellow);
>> >> > Plot(Status("LastVisibleBar"), "FVB", colorGreen);
>> >> > Plot(Status("LastVisibleBarIndex"), "FVBI", colorRed);
>> >> >
>> >> > --- In amibroker@yahoogroups.com, "wlandry01" <wlandry01@> wrote:
>> >> > >
>> >> > > Graham,
>> >> > >
>> >> > > I've seen conflicting comments on that point so I
>> >> > > checked the AFL reference for "Status" online.  It shows the
>> >> > > following;
>> >> > >
>> >> > > "firstvisiblebar", "lastvisiblebar", "firstvisiblebarindex",
>> >> > > "lastvisiblebarindex" - return bar number or bar index of
>> >> > > first/last visible bar. Available in indicator mode only.
>> >> > >
>> >> > > I used to think "firstvisiblebar" returned a "1", but it does,
>> >> > > apparently, return the bar number, as the following code
>> >> > > appears to work fine:
>> >> > >
>> >> > > HVC = Highest(ValueWhen(BarIndex() >= Status("FirstVisibleBar")
>> >> > > AND BarIndex() <= Status("LastVisibleBar"), Check));
>> >> > >
>> >> > > If you have more recent information, of if I've misinterpreted
>> >> > > something, please let me know as I've had some difficulty
>> >> > > completely understanding the Status indicators.
>> >> > >
>> >> > > Thanks,
>> >> > >
>> >> > >
>> >> > > Wayne
>> >> > >
>> >> > >
>> >> > >
>> >> > >
>> >> > >
>> >> > >
>> >> > >
>> >> > >
>> >> > >
>> >> > > --- In amibroker@yahoogroups.com, Graham <kavemanperth@> wrote:
>> >> > > >
>> >> > > > fistrvisiblebar returns a value of 1 on the first bar on
> screen.
>> >> > So you
>> >> > > > would need to use
>> >> > > lastvalue(valuewhen(status("firstvisiblebar"),barindex()))
>> >> > > >
>> >> > > > however I believe there is now status("firstvisiblebarindex")
>> >> > which will
>> >> > > > give you the value of barindex
>> >> > > >
>> >> > > >
>> >> > > >
>> >> > > > --
>> >> > > > Cheers
>> >> > > > Graham
>> >> > > > AB-Write >< Professional AFL Writing Service
>> >> > > > Yes, I write AFL code to your requirements
>> >> > > > http://e-wire.net.au/~eb_kavan/ab_write.htm
>> >> > > >
>> >> > > > On 01/09/06, wlandry01 <wlandry01@> wrote:
>> >> > > > >
>> >> > > > > Herman,
>> >> > > > >
>> >> > > > > Many thanks to you and all the others who provided input on
>> >> > this.
>> >> > > > > Sorry for the delay in responding but I decided to shut the
>> >> > > > > computer down while waiting for Ernesto to work his way
> through
>> >> > > > > South Florida.
>> >> > > > >
>> >> > > > > In any case, I now have my study working!  I do have a
> question,
>> >> > > > > however, on the code that you listed:
>> >> > > > >
>> >> > > > > Plot(C,"",1,128);
>> >> > > > > SetBarsRequired(1000000,1000000);
>> >> > > > > BlankBarsInRightMargin = 4;
>> >> > > > >
>> >> > > > > Plot(BarIndex()==Status("FirstVisibleBar"),"",5,styleArea|
>> >> > > > > styleOwnScale,-10,10);
>> >> > > > >
>> >> > > > > Plot(BarIndex()==Status("LastVisibleBar")-
>> >> > BlankBarsInRightMargin,"",
>> >> > > > > 4,styleArea|styleOwnScale,-10,10);
>> >> > > > >
>> >> > > > > When I chart this I get a light green line running from
> left to
>> >> > > > > right on the chart.  At the far left there's a small,
> vertical
>> >> > > > > green bar and on the far left there is a red bar.  On the far
>> >> > > > > right of the chart "0.00000" is shown in both red and green.
>> >> > > > > I've discovered that I can "separate" the red and green bars
>> >> > > > > (and lines) by adjusting the minimum and maximum setpoints.
>> >> > > > >
>> >> > > > > I don't understand, however, what generates the green line
>> >> > > > > between the two bars (or the red line, for that matter).
>> >> > > > > The Plot statement seems to call for a plot when BarIndex()
>> >> > > > > is equal to a specific value (the endpoints).  I reset the
>> >> > > > > Plot statement to show BarIndex()>=Status("FirstVisibleBar")
>> >> > > > > and the green bar expands to fill the entire screen,
> which makes
>> >> > > > > sense to me, but I don't see what's generating the line
> in the
>> >> > > > > original code.  Does the Plot statement assume a zero
> value if
>> >> > > > > the statement returns false?
>> >> > > > >
>> >> > > > > Thanks,
>> >> > > > >
>> >> > > > >
>> >> > > > > Wayne
>> >> > > > >
>> >> > > > >
>> >> > > > > --- In amibroker@yahoogroups.com, Herman <psytek@> wrote:
>> >> > > > > >
>> >> > > > > > Fred, my post did not refer to your code; your code is fine
>> >> > and does
>> >> > > > > > what it is supposed to do. I just outlined some
> problems one
>> >> > may
>> >> > > > > > encounter when working with First/LastVisibleBar.
>> >> > > > > >
>> >> > > > > > The problems I eluded to have all happened to me at one
> time
>> >> > or
>> >> > > another
>> >> > > > > > and resulted in a waste of my time. I use RT however I
> assume
>> >> > the
>> >> > > > > > problems can occur in EOD just the same. The problems can
>> >> > easily be
>> >> > > > > > confirmed by right-justifying your chart, running my code,
>> >> > > > > > adding/removing the SetBarsRequired() and/or changing the
>> >> > number of
>> >> > > > > > Blank bars in Preferences. You will note that
> LastVisibleBar
>> >> > marker
>> >> > > > > > appears and disappears depending on what one might have
>> >> > assumed
>> >> > > to be
>> >> > > > > > unrelated conditions.
>> >> > > > > >
>> >> > > > > > best regards,
>> >> > > > > > herman
>> >> > > > > >
>> >> > > > > > Fred wrote:
>> >> > > > > > > Herman,
>> >> > > > > > >
>> >> > > > > > > While I'd admit that the statement I posted really should
>> >> > take the
>> >> > > > > > > LastValue i.e.
>> >> > > > > > >
>> >> > > > > > > HVC = LastValue(Highest(ValueWhen(BarIndex() >= Status
>> >> > > > > > > ("FirstVisibleBar") AND BarIndex() <=
>> >> > > Status("LastVisibleBar"), C)));
>> >> > > > > > >
>> >> > > > > > > I don't follow the rest of your post ... With or without
>> >> > bars
>> >> > > in the
>> >> > > > > > > right margin I seem to get the correct result when HVC is
>> >> > > plotted ...
>> >> > > > > > >
>> >> > > > > > > Under what conditions do you not get the correct
> result ...
>> >> > > > > > >
>> >> > > > > > >
>> >> > > > > > >
>> >> > > > > > >
>> >> > > > > > >
>> >> > > > > > >
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>> >> > > > > > > http://www.amibroker.com/support.html
>> >> > > > > > >
>> >> > > > > > >
>> >> > > > > > > Yahoo! Groups Links
>> >> > > > > > >
>> >> > > > > > >
>> >> > > > > > >
>> >> > > > > > >
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>> >> > > > > > >
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