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I stand corrected. Last time I looked at AMA that wasn't there. Yes it
was a long time ago.
--
Cheers
Graham Kav
AFL Writing Service
http://www.aflwriting.com
2008/9/19 Tomasz Janeczko <groups@xxxxxxxxxxxxx>:
> Graham,
>
> I am endlessly surprised when people say they could not found
> the description when it sits under F1 key.
> Type AMA in the AFL editor and press F1 key.
> ==================================
> You don't need to search at all. Just press F1.
>
> So AMA *IS* described to the level of every single bit in (of course) the User's Guide
> AFL function reference, available from F1 key in the AFL editor.
> http://www.amibroker.com/guide/afl/afl_view.php?ama
>
> (see comment that provides actual looping EQUIVALENT for AMA).
>
> Best regards,
> Tomasz Janeczko
> amibroker.com
> ----- Original Message -----
> From: "Graham" <kavemanperth@xxxxxxxxx>
> To: <amibroker@xxxxxxxxxxxxxxx>
> Sent: Friday, September 19, 2008 10:14 AM
> Subject: Re: [amibroker] Re: Recursive Boolean Expressions... Possible?
>
>
>> Generally speaking, if your variable requires a previous value of that
>> variable to determine current value then you need to use a loop
>> Other areas that can require looping is items such as trail stops,
>> where a subsequent Buy true condition can reset the trail price levels
>> to that newer bar
>>
>>
>> Of course there are built in functions that can do this within the
>> limits of their capabilities, eg AMA
>>
>> In the case of this thread it was not entirely clear just having the
>> line of code as to what the intent was
>> var = condition AND NOT ref(var,-6); could be interpreted differently as either
>> var = condition and not ref(condition,-6) or in its raw state
>> in the raw state as shown it does require looping.
>> AMA function was mentioned somewhere in the thread, not even sure if
>> to say that it can be used for this. I am not at all clear on using
>> AMA as I have not yet found a description of exactly what the
>> algorithm is, I have only ever found examples of putting values into
>> it.
>>
>>
>> --
>> Cheers
>> Graham Kav
>> AFL Writing Service
>> http://www.aflwriting.com
>>
>>
>>
>> 2008/9/19 sidhartha70 <sidhartha70@xxxxxxxxx>:
>>> In answer to your question Brian, I ended up using a loop.
>>> Seeing the power of AFL, I often find myself resisting the use of
>>> loops, but then wrestling with the neccessary code to achieve my goals
>>> without using a loop.
>>> This seems to be a problem I hit quite consistently... which is a
>>> general uncertainty about whether I can achieve what I want without a
>>> loop or not. As it goes I usually waste time in that minor feedback
>>> loop for a while!!!
>>>
>>>
>>> --- In amibroker@xxxxxxxxxxxxxxx, "brianw468" <wild21@xxx> wrote:
>>>>
>>>> Thanks "GP", but I think your latest contribution muddies the waters
>>>> a bit. My understanding of the original question is that varx would
>>>> always be boolean - ie 1 or 0 (True or False)whereas your example
>>>> treats it as an integer variable.
>>>> The issue revolves around the real question - ie is the questioner
>>>> asking if a single line statement can contain a recursive element
>>>> (answer is probably NO) - or is the aim to solve a particular coding
>>>> problem without using a loop, where the answer could well be that
>>>> there are work-arounds. The guy who started this thread should
>>>> clarify what he is trying to do. Otherwise, further discussion is a
>>>> bit pointless.
>>>>
>>>> Brian
>>>>
>>>> --- In amibroker@xxxxxxxxxxxxxxx, "gp_sydney" <gp.investment@>
>>>> wrote:
>>>> >
>>>> > Brian,
>>>> >
>>>> > As you say, it depends on what the original intention was. There are
>>>> > two ways to interpret a statement like:
>>>> >
>>>> > varx = Ref(varx,-1) + 1;
>>>> >
>>>> > The first is the way it actually works now, where each element in
>>>> the
>>>> > new varx is the previous element in the old varx incremented by one.
>>>> > So if the original varx array has:
>>>> >
>>>> > varx[10] = 1
>>>> > varx[11] = 27
>>>> > varx[12] = 39
>>>> > varx[13] = 102
>>>> >
>>>> > The new varx array will have:
>>>> >
>>>> > varx[11] = 2
>>>> > varx[12] = 28
>>>> > varx[13] = 40
>>>> > varx[14] = 103
>>>> >
>>>> > The other way, which is what I was talking about (as I thought it
>>>> was
>>>> > what was being asked about), is where the value at each bar is
>>>> updated
>>>> > iteratively bar by bar as it would be in a loop. So if we assume
>>>> that
>>>> > varx[10] is still one (but it would depend on what came before),
>>>> then
>>>> > we would end up with:
>>>> >
>>>> > varx[11] = 2 (1+1)
>>>> > varx[12] = 3 (2+1)
>>>> > varx[13] = 4 (3+1)
>>>> > varx[14] = 5 (4+1)
>>>> >
>>>> > This is equivalent to the loop code:
>>>> >
>>>> > varx[i] = varx[i-1] + 1;
>>>> >
>>>> > Regards,
>>>> > GP
>>>> >
>>>> >
>>>> > --- In amibroker@xxxxxxxxxxxxxxx, "brianw468" <wild21@> wrote:
>>>> > >
>>>> > > Hi,
>>>> > > Can you not solve the problem by (effectively) re-defining varx
>>>> > > within the expression i.e.
>>>> > >
>>>> > > varx = C<Ref(L,-6) AND vary <6 AND NOT(C<Ref(L,-12) AND vary <6);
>>>> > >
>>>> > > Haven't tried this and the presentation could possibly be tidied
>>>> a
>>>> > > bit. (Depending on what, exactly, you are trying to achieve, the
>>>> very
>>>> > > last term might need to be "Ref(vary,-6)<6" or some such.
>>>> > >
>>>> > > Brian
>>>> > >
>>>> > >
>>>> > > --- In amibroker@xxxxxxxxxxxxxxx, "Tomasz Janeczko" <groups@>
>>>> > > wrote:
>>>> > > >
>>>> > > > It depends. The loop is general-purpose solution and works
>>>> always.
>>>> > > >
>>>> > > > In some cases loops can be eliminated using Cum(), ValueWhen(),
>>>> > > > AMA, AMA2.
>>>> > > >
>>>> > > > Best regards,
>>>> > > > Tomasz Janeczko
>>>> > > > amibroker.com
>>>> > > > ----- Original Message -----
>>>> > > > From: "sidhartha70" <sidhartha70@>
>>>> > > > To: <amibroker@xxxxxxxxxxxxxxx>
>>>> > > > Sent: Thursday, September 18, 2008 9:56 AM
>>>> > > > Subject: [amibroker] Re: Recursive Boolean Expressions...
>>>> Possible?
>>>> > > >
>>>> > > >
>>>> > > > > Can I ask the master...?? TJ... Does this kind of expression
>>>> > > > > absolutely require a loop structure?
>>>> > > > >
>>>> > > > > TIA
>>>> > > > >
>>>> > > > > --- In amibroker@xxxxxxxxxxxxxxx, "gp_sydney"
>>>> <gp.investment@>
>>>> > > wrote:
>>>> > > > >>
>>>> > > > >> Graham,
>>>> > > > >>
>>>> > > > >> That doesn't work either, in the general case, as varx is
>>>> still
>>>> > > not
>>>> > > > >> dependent on previous values of varx, only on previous
>>>> values of
>>>> > > your
>>>> > > > >> first "temp" statement.
>>>> > > > >>
>>>> > > > >> Consider the simpler case:
>>>> > > > >>
>>>> > > > >> temp = BarIndex() < 10;
>>>> > > > >> varx = temp AND NOT Ref(temp,-1);
>>>> > > > >>
>>>> > > > >> temp now has the first 10 bars set to one and all other bars
>>>> set
>>>> > > to
>>>> > > > >> zero. varx will have the first 11 bars set to zero, since Ref
>>>> > > (temp,-1)
>>>> > > > >> is one (actually the first bar will probably be null) and
>>>> then
>>>> > > all
>>>> > > > >> subsequent bars will also be zero since temp is then zero.
>>>> > > > >> Consequently, varx would be completely zero, except perhaps
>>>> for
>>>> > > the
>>>> > > > >> first null.
>>>> > > > >>
>>>> > > > >> Assuming this did work as suggested, compare to:
>>>> > > > >>
>>>> > > > >> varx = BarIndex() < 10 AND NOT Ref(varx,-1);
>>>> > > > >>
>>>> > > > >> Actually if the first bar was null due to Ref(varx,-1) being
>>>> > > null,
>>>> > > > >> then varx would end up completely full of nulls (a problem
>>>> to be
>>>> > > wary
>>>> > > > >> of with nulls in loops). But say the first bar ended up
>>>> being
>>>> > > zero
>>>> > > > >> (perhaps the nz function was used), then the second bar
>>>> would be
>>>> > > one,
>>>> > > > >> since BarIndex is less than 10 and Ref(varx,-1) refers to
>>>> the
>>>> > > first
>>>> > > > >> bar which we just said was zero. The third bar would be
>>>> zero,
>>>> > > since
>>>> > > > >> Ref(varx,-1) now refers to the second bar which we just set
>>>> to
>>>> > > one,
>>>> > > > >> and the fourth bar would be one again. This would continue
>>>> up to
>>>> > > the
>>>> > > > >> 10th bar, after which all bars would be zero due to the
>>>> BarIndex
>>>> > > term.
>>>> > > > >> The first 10 bars of varx alternating between one and zero
>>>> make
>>>> > > the
>>>> > > > >> result different to the first version.
>>>> > > > >>
>>>> > > > >> Regards,
>>>> > > > >> GP
>>>> > > > >>
>>>> > > > >>
>>>> > > > >> --- In amibroker@xxxxxxxxxxxxxxx, Graham <kavemanperth@>
>>>> wrote:
>>>> > > > >> >
>>>> > > > >> > try this
>>>> > > > >> > temp = C<Ref(L,-6) AND vary<6;
>>>> > > > >> > varx = temp AND NOT Ref(temp ,-6);
>>>> > > > >> >
>>>> > > > >> > --
>>>> > > > >> > Cheers
>>>> > > > >> > Graham Kav
>>>> > > > >> > AFL Writing Service
>>>> > > > >> > http://www.aflwriting.com
>>>> > > > >> >
>>>> > > > >> >
>>>> > > > >> >
>>>> > > > >> >
>>>> > > > >> > 2008/9/18 gp_sydney <gp.investment@>:
>>>> > > > >> > > No, you can't do that as the right-hand expression is
>>>> > > evaluated
>>>> > > > > on the
>>>> > > > >> > > whole array before anything is assigned to the left-hand
>>>> > > variable.
>>>> > > > >> > > That means that "varx" is effectively constant during
>>>> the
>>>> > > expression
>>>> > > > >> > > evaluation for the whole array. It's essentially the
>>>> same as:
>>>> > > > >> > >
>>>> > > > >> > > temp = IIf(C<Ref(L,-6) AND vary<6 AND NOT Ref(varx,-
>>>> > > 6),True,False);
>>>> > > > >> > > varx = temp;
>>>> > > > >> > >
>>>> > > > >> > > To do what you are suggesting would require a loop.
>>>> > > > >> > >
>>>> > > > >> > > Regards,
>>>> > > > >> > > GP
>>>> > > > >> > >
>>>> > > > >> > >
>>>> > > > >> > > --- In amibroker@xxxxxxxxxxxxxxx, "sidhartha70"
>>>> > > <sidhartha70@>
>>>> > > > > wrote:
>>>> > > > >> > >>
>>>> > > > >> > >> Hi All,
>>>> > > > >> > >>
>>>> > > > >> > >> Is it possible to have recursive boolean
>>>> expressions...?
>>>> > > i.e. the
>>>> > > > >> true
>>>> > > > >> > >> or false of the current value of the array depends on
>>>> > > whether a
>>>> > > > >> > >> previous value of the array is true or false.
>>>> > > > >> > >>
>>>> > > > >> > >> So for example,
>>>> > > > >> > >>
>>>> > > > >> > >> varx = IIf(C<Ref(L,-6) AND vary<6 AND NOT Ref(varx,-
>>>> > > 6),True,False);
>>>> > > > >> > >>
>>>> > > > >> > >> Would that work... or are recursive booleans like this
>>>> not
>>>> > > > > allowed??
>>>> > > > >> > >>
>>>> > > > >> > >> TIA
>>>> > > > >> > >>
>>>> > > > >> >
>>>> > > > >>
>>>> > > > >
>>>> > > > >
>>>> > > > >
>>>> > > > > ------------------------------------
>>>> > > > >
>>>> > > > > Please note that this group is for discussion between users
>>>> only.
>>>> > > > >
>>>> > > > > To get support from AmiBroker please send an e-mail directly
>>>> to
>>>> > > > > SUPPORT {at} amibroker.com
>>>> > > > >
>>>> > > > > For NEW RELEASE ANNOUNCEMENTS and other news always check
>>>> DEVLOG:
>>>> > > > > http://www.amibroker.com/devlog/
>>>> > > > >
>>>> > > > > For other support material please check also:
>>>> > > > > http://www.amibroker.com/support.html
>>>> > > > > Yahoo! Groups Links
>>>> > > > >
>>>> > > > >
>>>> > > > >
>>>> > > >
>>>> > >
>>>> >
>>>>
>>>
>>>
>>>
>>> ------------------------------------
>>>
>>> Please note that this group is for discussion between users only.
>>>
>>> To get support from AmiBroker please send an e-mail directly to
>>> SUPPORT {at} amibroker.com
>>>
>>> For NEW RELEASE ANNOUNCEMENTS and other news always check DEVLOG:
>>> http://www.amibroker.com/devlog/
>>>
>>> For other support material please check also:
>>> http://www.amibroker.com/support.html
>>> Yahoo! Groups Links
>>>
>>>
>>>
>>>
>>
>> ------------------------------------
>>
>> Please note that this group is for discussion between users only.
>>
>> To get support from AmiBroker please send an e-mail directly to
>> SUPPORT {at} amibroker.com
>>
>> For NEW RELEASE ANNOUNCEMENTS and other news always check DEVLOG:
>> http://www.amibroker.com/devlog/
>>
>> For other support material please check also:
>> http://www.amibroker.com/support.html
>> Yahoo! Groups Links
>>
>>
>>
>
> ------------------------------------
>
> Please note that this group is for discussion between users only.
>
> To get support from AmiBroker please send an e-mail directly to
> SUPPORT {at} amibroker.com
>
> For NEW RELEASE ANNOUNCEMENTS and other news always check DEVLOG:
> http://www.amibroker.com/devlog/
>
> For other support material please check also:
> http://www.amibroker.com/support.html
> Yahoo! Groups Links
>
>
>
>
------------------------------------
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