As far as For .vs. Sum is concerned ...
The AFL below will demonstrate that the first 6 digits are the
same ... and the 7th is close ...
BI = BarIndex();
LVBI = LastValue(BI);
XBI = (BI * 0.00001) ^ 0.987654321;
SumXBI = Sum(XBI, 100);
forXBI = Cum(0);
for (i = LVBI - 99; i <= LVBI; i++)
{
forXBI[LVBI] = forXBI[LVBI] + XBI[i];
}
Filter = BI == LVBI;
AddColumn(XBI, "XBI", 1.9);
AddColumn(SumXBI, "SumXBI", 1.9);
AddColumn(forXBI, "ForXBI", 1.9);
--- In amibroker@yahoogroups.com, "Fred" <[EMAIL PROTECTED]> wrote:
>
> I agree completely with #1 ...
>
> --- In amibroker@yahoogroups.com, "Tom Tom" <michel_b_g@> wrote:
> >
> > Thanks Paul and Ed.
> >
> > It is a shame because i manage to code AR Burg method all in AFL
> native.
> > Two points are not so good in my coding :
> >
> > 1- Loop for need to flip an array. There is no such function in
> native AFL,
> > but it is very usefull sometimes for many algorythm.
> > Exemple : [1 5 4 8] -> [8 4 5 1]
> > Is there a way do do it without loop ? (if not possible thomas
you
> cannot
> > add a function flip_array ? very usefull for all lattice filter
or
> backwards
> > recursion)
> >
> > Code :
> > for (j = 1; j < i; j++) a_old_flip[j] = a_old[i-j];
> >
> > 2- Precision digit make many sensitive algorythm not done by
AFL.
> Bu i think
> > it is done to have full speed from AB, so great.
> > But I have not the same result for SUM and FOR(i=0,...)
> >
> > Code :
> >
> > AFL SUM function :
> > Num = 0; Den = 0;
> > Num = Sum(W*f*b_shifted, LongBar - i);
> > Den = Sum(W*(f^2 + b_shifted^2), LongBar - i);
> > k[i] = 2*Num[LongBar - 1]/Den[LongBar - 1];
> >
> > FOR :
> > Num = 0; Den = 0;
> > for (j = i; j < LongBar; j++) {
> > Num = Num + 100000*W[j]*( f[j]*b[j-1] );
> > Den = Den + 100000*W[j]*( f[j]^2 + b[j-1]^2 );
> > }
> > k[i] = 2*Num/Den;
> >
> > I have not the same result for the number k[i] !?
> > For small number on small period formula give back same
result...
> but for
> > long periods... i end up with slightly different number (and for
> AR coef, it
> > means big diff... arhhh).
> > which is better SUM or FOR (I had to test by coding it in
JSscript
> or
> > VBscript and compare maybe) ?
> >
> > Thanks again.
> >
> > Cheers,
> > Mich.
> >
> >
> >
> >
> > ----- Original Message -----
> > From: Ed Hoopes
> > To: amibroker@yahoogroups.com
> > Sent: Thursday, November 16, 2006 5:17 PM
> > Subject: [amibroker] Re: Digit precision on AB ?
> >
> >
> > Also, the default precision in javascript is double.
> >
> > --- In amibroker@yahoogroups.com, "Paul Ho" .> wrote:
> > >
> > >you can only doing single precision floating points within AFL
> all
> > >functions that I called returned single precision, 1. I thought
> it was 8
> > >significant digits
> > >http://en.wikipedia.org/wiki/IEEE_754;
> > >2. yes or dll
> > >3. for and sum should give the same answer.
> > >cheers
> > >Paul.
> > >
> > >_____
> > >
> > >From: amibroker@yahoogroups.com
[mailto:[EMAIL PROTECTED]
> > On Behalf
> > >Of Tom Tom
> > >Sent: Thursday, 16 November 2006 7:01 PM
> > >To: amibroker@yahoogroups.com
> > >Subject: [amibroker] Digit precision on AB ?
> > >
> > >
> > >
> > >Hello,
> > >
> > >Does someone can help me about digit precision on AB please.
> > >
> > >1- I think it is 7 signifiant digit +exposant +signe. Am i
right ?
> > >
> > >2- For more precision we need to code in VBscript and enable
> double
> > float ?
> > >
> > >3- But if i prefer stay on Amibroker AFL. For a sum loop for
> exemple, i
> > >didn't have same result with looping with FOR(i=...) and with
> > SUM(array,
> > >periods). SUM is better ? Native AFL included function work
inside
> > with only
> > >
> > >7 digit precision too, or they work in more precision and send
> back
> > function
> > >
> > >result in 7 digit format. If it is the case, SUM should give
> better
> > calcul
> > >accuracy than FOR(i=...) ?
> > >
> > >Thanks,
> > >Mich.
> > >
> > >__________________________________________________________
> > >Windows Live Messenger sur i-modeT : dialoguez avec vos amis
> depuis
> > votre
> > >mobile comme sur PC ! http://mobile.
> > ><http://mobile.live.fr/messenger/bouygues/>
> live.fr/messenger/bouygues/
> > >
> >
> >
> >
> >
> > _________________________________________________________________
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> >
>
