Thanks for your input on this chaps. Certainly cleared some fog in my head. All sorted now.
--- In amibroker@yahoogroups.com, "gp_sydney" <[EMAIL PROTECTED]> 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@yahoogroups.com, "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@yahoogroups.com, "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@yahoogroups.com> > > > 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@yahoogroups.com, "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@yahoogroups.com, 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@yahoogroups.com, "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! 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