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Given that this same question gets asked over and over again, it might
be worth adding an example to that tutorial explicitly illustrating
what would happen in a self referencing calculation.
Yes, many people simply have not read the tutorial. But for those that
have, it would seem that a significant percentage of readers still do
not realize that a temporary array is being created in that situation.
Mike
--- In amibroker@xxxxxxxxxxxxxxx, "Tomasz Janeczko" <groups@xxx>
wrote:
>
> It is easy to understand, if only you READ THE
> tutorial section of the guide:
>
> http://www.amibroker.com/guide/h_understandafl.html
>
> All tutorial is must-read.
> =================
>
> People are crying for help while in fact
> everything you need to read is in the TUTORIAL section
> of the guide.
> This single short section of the tutorial
> http://www.amibroker.com/guide/h_understandafl.html
>
> is absolute must-read and should be read and repeated.
>
> Best regards,
> Tomasz Janeczko
> amibroker.com
> ----- Original Message -----
> From: "ian_rosbif" <ian_rosbif@xxx>
> To: <amibroker@xxxxxxxxxxxxxxx>
> Sent: Tuesday, November 18, 2008 6:52 PM
> Subject: [amibroker] Re: What is wrong with these 3 lines of code?
>
>
> > You're not dumb, it is rather difficult to understand! Using your
> > example and assuming 11 bars in each array:
> > Before the 1st statement, auxCrossedIntermed = "00000000000",
> > After the 1st statement, auxCrossedIntermed = "00000000010"
> >
> > Before the 2nd statement, CrossedIntermed = "00000000000",
> > and Ref(CrossedIntermed, -1) = "0000000000"... Amibroker
effectivley
> > treats the Ref... part of the statement as if it was a temporary
copy
> > of the CrossedIntermed statement taken before the 2nd statement
began
> > execution (note that there are only 10 elements in this copy
array).
> > Changes made to CrossIntermed during the 2nd statement by moving
> > values from AuxCrossedIntermed are not reflected in the copy
array.
> > therefore the Ref... clause always copies zero in this scenario.
> >
> > I hope this clarifies it, but as I said before, the same thing got
me
> > when I first started out with AB...took me a couple of weeks to
> > finally realise what was going on.
> >
> >
> > --- In amibroker@xxxxxxxxxxxxxxx, "nunopires2001" <nunopires2001@>
> > wrote:
> >>
> >> Thanks for the answer.
> >>
> >> To be honest, i am feeling really dumb, since i didn't understand
> > the
> >> explanation.
> >>
> >> Please suppose the following scenario:
> >>
> >> Low[9]=950
> >> Intermed[9]=970
> >> High[9]=1000
> >>
> >> auxCrossedIntermed=IIf(Low< Intermed AND High> Intermed,1,0);
> >> CrossedIntermed=auxCrossedIntermed OR Ref(CrossedIntermed,-1);
> >>
> >> On the bar #10, how will Amibroker evaluate the second formula?
> >> During the evaluation, what will be the values for
> > auxCrossedIntermed
> >> and Ref(CrossedIntermed,-1) ?
> >>
> >>
> >> Best Regards!
> >>
> >>
> >> --- In amibroker@xxxxxxxxxxxxxxx, "ian_rosbif" <ian_rosbif@>
wrote:
> >> >
> >> > Hi,
> >> > Are you trying use "...OR Ref(CrossedIntermed,-1);" to get the
> > cross
> >> > to persist in CrossedIntermed? In other words, if the cross
> > occurs at
> >> > 11:45, the following 15 elements of Crossintermed should be "1"
> > until
> >> > 12:01, when they should then all have "666" in them?
> >> >
> >> > In which case, the problem lies with the "circular" nature of:
> >> > >>CrossedIntermed=auxCrossedIntermed OR Ref(CrossedIntermed,-
1);
> >> >
> >> > auxCrossedIntermed will have a combination of 1s & 0s in it,
but
> >> > these aren't actually "moved" to Crossedintermed until the
> > statement
> >> > hase been fully evaluated. Therefore Ref(Crossedintermed, -1)
> > will
> >> > always evaluate to 0 at the time it's executed, even though the
1
> >> > appears in the array element representing the cross event after
> > the
> >> > statement has been executed.
> >> >
> >> > This is something that drove me mad before I cottoned onto it.
> >> > maybe this would work:
> >> >
> >> > // initialise final values
> >> > CrossedIntermed=IIf(TimeNum()>120000, 666, 0);
> >> > // set cross events
> >> > auxCrossedIntermed=IIf(Low< Intermed AND High> Intermed, 1, 0);
> >> > // cross persists for whole day after it occurs once
> >> > auxCrossedIntermed = Flip(auxCrossedIntermed, True==False);
> >> > // finalise values
> >> > CrossedIntermed=IIf(TimeNum()>120000, 666, auxCrossedIntermed);
> >> >
> >> > If you want the "1" to persist after midday, change the last
> >> > statement to:
> >> > CrossedIntermed=IIf(auxCrossedIntermed, auxCrossedIntermed,
> >> > CrossedIntermed);
> >> >
> >> >
> >> > --- In amibroker@xxxxxxxxxxxxxxx, "nunopires2001"
> > <nunopires2001@>
> >> > wrote:
> >> > >
> >> > > Hello,
> >> > >
> >> > > After a encouraging start with Amibroker, i am realizing that
> >> > writing
> >> > > code on AFL is not all that simple...
> >> > >
> >> > > Anyone can explain me what is wrong with these lines of code?
> >> > >
> >> > > CrossedIntermed=0;
> >> > > auxCrossedIntermed=IIf(Low< Intermed AND High>
> > Intermed,1,0);
> >> > > CrossedIntermed=auxCrossedIntermed OR
Ref(CrossedIntermed,-
> > 1);
> >> > >
CrossedIntermed=IIf(TimeNum()>120000,666,CrossedIntermed);
> >> > >
> >> > > I am working with intraday, 1min data. The market opens at
> > 110000
> >> > and
> >> > > closes at 193000.
> >> > >
> >> > > I just want to check the CrossedIntermed Value after 12.00h,
> > and the
> >> > > value returned should be:
> >> > > -> 1: If the security crossed Intermed
> >> > > -> 0: Otherwise
> >> > > -> 666: If TimeNum()>120000
> >> > >
> >> > >
> >> > > Thanks alot!
> >> > >
> >> >
> >>
> >
> >
> >
> > ------------------------------------
> >
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> >
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> >
>
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