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Dimitris,
You are welcome. By the way, you may be interested in the recent article
in Stocks&Commodities (11/2003) that I have written Traders Tips for.
(http://www.amibroker.com/members/)
The author (Spyros Raftopoulos) presented zig zag validity technique very similar to one that you have presented
months ago on AmiBroker mailing list.
Best regards,
Tomasz Janeczko
amibroker.com
----- Original Message -----
From: "DIMITRIS TSOKAKIS" <TSOKAKIS@xxxxxxxxx>
To: <amibroker@xxxxxxxxxxxxxxx>
Sent: Wednesday, October 15, 2003 10:38 PM
Subject: [amibroker] Re: MA, DEMA and TEMA can take array parameters, but EMA can't?
> Tomasz,
> thank you for the explanations [and the interesting ref].
> I have no misunderstanding about the recursive mechanism of AMA etc.
> --- In amibroker@xxxxxxxxxxxxxxx, "Tomasz Janeczko" <amibroker@xxxx>
> wrote:
> > Dimitris,
> >
> > Yes we can call them equivalent because Wilders( array, 1/x)
> function uses
> > exactly the same formula as AMA( array, 1/ x):
> >
> > WildersToday = ( Array + ( Periods - 1 ) * WildersYesterday ) /
> Periods.
> >
> > This is mathematically strictly the same as:
> >
> > WildersToday = Array * ( 1/ Periods ) + (1 - (1/Periods) ) *
> WildersYesterday;
> >
> > Now AMA is:
> >
> > AMAToday = Array * Factor + (1-Factor) * AMAYesterday
> >
> > When Factor = 1/periods those two are mathematically strictly
> equivalent.
> >
> > There is no magic, just pure math.
> >
> > It does not really matters if Factor is variable or not because the
> formula
> > is constant.
>
> This is exactly my point : A formula may be constant [the same] but
> the procedure may be meaningless.
> The y=x^2-2 is well defined in integers, rationals and real numbers,
> the solution of x^2-2=0 is N/A for integers or rationals.
> We may have, in AFL, variable per for MA(C,per), but what is the
> meaning ?
> The definition of a 10-bar MA is
> MA(C,10)=sum(C,10)/10
> After this, the MA(C,9.3) is meaningless.
> Now, if we make an internal agreement and "define" for every x,
> 9<=x<10 the MA(C,x) equal to MA(C,9), then we say that we have
> variable MA but it is not true, it does not fit to the definition of
> MA.
> So, before looking at the maths, we have to give some meaning to this
> variable period for Wilders, EMA etc.
> This is my point, if a variable per MA, EMA exists or not.
> We can not transfer in T/A the continuous functions without some
> special [and usually not declared] agreement, T/A time is not
> continuous, the beatiful continuous lines we see are nothing but
> illusions, the real thing is discrete dots without the intermediate
> points. You, as a creator, use a special technique to give us
> these "continuous" lines. And you need this technique, because your
> initial material is discontinuous [and a bit ugly...].
> The continuous lines we see in an RSI graph is not a proof that our
> RSI arrays are continuous and it should be clear.
> Thank you for the interesting dialogue, I will revert when you
> implement the variable period EMA in some future AFL edition.
> Now, it would be better to come back to the final tests of the most
> interesting Equity Inspection Points application.
> Dimitris Tsokakis
>
> > You are making false assumption thinking that
> >
> > evenbar = BarIndex()%2 == 0;
> >
> > AMA( C, IIF( evenbar, 10, 11 ) )
> >
> > will work like
> >
> > IIF( evenbar, AMA( C, 10 ), AMA( C,11 ) )
> >
> > but this is just that - false assumption. You assume that
> > switching periods would cause all calculations to start from the
> very beginning,
> > but it is not the case.
> > As for analogy: it is well known thing in electroacustics.
> >
> > The EMA (AMA, etc) is single pole recursive low pass filter aka
> > as infinite impulse response filter (IIR)
> >
> http://www.ece.utexas.edu/~bevans/courses/realtime/lectures/06_IIR_Fil
> ters/lecture6.pdf
> >
> >
> > If you have PHYSICAL single pole low pass filter (for example
> simple RC or LC circuit) and you change
> > the 'cut-off' frequency (by changing capacity of condenser for
> example)
> > then you are not able to 'start from the beginning'
> > because physical filter has it's state and if you change
> > the parameters these parameters are applied to current state.
> > This is *exactly* how variable period AMA works.
> > AMA and others work in 'real time'. They preserve its state
> (previous value of AMA)
> > and apply parameters (smoothing factor) to produce next value.
> Exactly like physical circuit.
> > Physical RC circuit can not go back and take the series voltage
> numbers from past year to calculate
> > todays value. It just remembers its current state.
> > Exactly the same AMA - all it needs is CURRENT data (price) and its
> previous state (single number
> > representing previous value of AMA). It does not re-start
> calculations from the very beginning, ever.
> >
> > And this is fundamentally different from FIR filter (Finite impulse
> > response) like MA that is re-calculated for N-bars, not for
> infinite number of bars.
> >
> > Best regards,
> > Tomasz Janeczko
> > amibroker.com
> > ----- Original Message -----
> > From: "DIMITRIS TSOKAKIS" <TSOKAKIS@xxxx>
> > To: <amibroker@xxxxxxxxxxxxxxx>
> > Sent: Wednesday, October 15, 2003 2:47 PM
> > Subject: [amibroker] Re: MA, DEMA and TEMA can take array
> parameters, but EMA can't?
> >
> >
> > > Tomasz,
> > > I clearly understand the recursive nature of these functions.
> > > This is not the subject.
> > > The question is : Can we call "equivalent" two never touching
> lines ?
> > > It is somehow tricky to ask from the user to accept the following
> > > story:
> > > 1. Wilders(C,x) is N/A for variable x
> > > 2. For fixed x the Wilders(C,x)=AMA(C,1/x) is true
> > > 3. Please accept the "analog" meaning for the argument
> > > Arg. 1 : Wilders(C,x) is *also* AMA(C,1/x) *even when* x is
> variable
> > > or
> > > Arg. 2 : You may call AMA(C,1/x) as Wilders(C,x), x variable,
> > > *because* AMA(C,1/x) *is* Wilders(C,x), when x=fixed !!
> > >
> > > We have no evidence that this "analogy" exists and, form my
> experiece
> > > in Physics, it is dangerous to speak [and use] for analogies just
> > > because we like them.
> > > >From this point of view, it is better not to have variable
> periods
> > > for EMA, Wilders. Now, AMA(C,1/x) , 10<=x<=20 is an interesting
> > > line "between" AMA(C,1/10) and AMA(C,1/20) and this could be the
> > > happy end of the story. If someone needs to call it Wilders with
> > > variable period, it is OK, but there is no evidence to do it.
> > > Dimitris Tsokakis
> > > --- In amibroker@xxxxxxxxxxxxxxx, "Tomasz Janeczko"
> <amibroker@xxxx>
> > > wrote:
> > > > Dimitris,
> > > >
> > > > The explanation should be obvious to someone with the deep
> > > background
> > > > in physics and mathematics as you.
> > > >
> > > > The reason is that AMA, EMA, TEMA, DEMA, Wilders
> > > > are all recursive functions. See
> > > > http://www.amibroker.com/guide/afl/afl_view.php?name=AMA
> > > > and
> > > > http://www.amibroker.com/guide/afl/afl_view.php?name=DEMA
> > > >
> > > > for detailed recursive algorithm.
> > > >
> > > > What does it mean? It means that current value depends
> > > > on input data array and PREVIOUS value of the indicator.
> > > > The PREVIOUS value includes the value of "previous-previous"
> value
> > > > and so on.
> > > > Now if you change the period every bar all these changes (for
> all
> > > previous bars)
> > > > affect current bar value and that's why variable period AMA is
> > > smooth and
> > > > does not jump from Wilders10-Wilders11.
> > > >
> > > > Best regards,
> > > > Tomasz Janeczko
> > > > amibroker.com
> > > > ----- Original Message -----
> > > > From: "DIMITRIS TSOKAKIS" <TSOKAKIS@xxxx>
> > > > To: <amibroker@xxxxxxxxxxxxxxx>
> > > > Sent: Wednesday, October 15, 2003 1:36 PM
> > > > Subject: [amibroker] Re: MA, DEMA and TEMA can take array
> > > parameters, but EMA can't?
> > > >
> > > >
> > > > > Tomasz,
> > > > > How do we understand this equivalence ?
> > > > > x=10+(Cum(1)%11);
> > > > > is equal to 10 every 11 bars.
> > > > > The
> > > > > Wp=10;Plot(Wilders(C,Wp),"Wilders",1,1);
> > > > > and
> > > > > Plot(AMA(C,1/x),"AMA",7,8);
> > > > > do not touch every 11 bars...
> > > > > The same with Wilders(c,20).
> > > > > See, for example the
> > > > >
> > > > > x=10+(Cum(1)%11);
> > > > > Wp10=10;Plot(Wilders(C,Wp10),"Wilders10",1,1);
> > > > > Wp20=20;Plot(Wilders(C,Wp20),"Wilders20",1,1);
> > > > > Plot(AMA(C,1/X),"AMA",7,1);
> > > > > Plot(AMA(C,1/10),"AMA 1/10",4,8);
> > > > > Plot(AMA(C,1/20),"AMA 1/20",4,8);
> > > > >
> > > > > AMA(C,1/10) is 1-1 equivalent to Wilders(C,10).
> > > > > On the other side, AMA(C,1/X) touches only by coincidence the
> > > Wp10 or
> > > > > Wp20.
> > > > >
> > > > > Dimitris Tsokakis
> > > > > --- In amibroker@xxxxxxxxxxxxxxx, "Tomasz Janeczko"
> > > <amibroker@xxxx>
> > > > > wrote:
> > > > > > Stephane,
> > > > > >
> > > > > > That's true but Wilders is nothing more nothing less than
> just
> > > AMA
> > > > > > with 1/n smoothing factor.
> > > > > >
> > > > > > Wilders( array, N ) =>>> AMA( array, 1 / N )
> > > > > >
> > > > > >
> > > > > > Best regards,
> > > > > > Tomasz Janeczko
> > > > > > amibroker.com
> > > > > > ----- Original Message -----
> > > > > > From: "Stephane Carrasset" <nenapacwanfr@xxxx>
> > > > > > To: <amibroker@xxxxxxxxxxxxxxx>
> > > > > > Sent: Wednesday, October 15, 2003 1:03 PM
> > > > > > Subject: [amibroker] Re: MA, DEMA and TEMA can take array
> > > > > parameters, but EMA can't?
> > > > > >
> > > > > >
> > > > > > > Hi, Dimitri,
> > > > > > >
> > > > > > > Wilders does not accept variable period
> > > > > > >
> > > > > > > Plot(Wilders(C,RSI(3)),"",2,1);
> > > > > > >
> > > > > > > return a bad argument
> > > > > > >
> > > > > > > stepghane
> > > > > > >
> > > > > > >
> > > > > > > <nenapacwanfr@xxxx> wrote:
> > > > > > > > Dimitri,
> > > > > > > >
> > > > > > > > I didn't know that wilders accept variable period...
> > > > > > > > Thanks
> > > > > > > >
> > > > > > > > Stephane
> > > > > > > >
> > > > > > > > > Dave,
> > > > > > > > > I have posted in the files section the varPER.txt
> with
> > > the
> > > > > EMA,
> > > > > > > AMA
> > > > > > > > > and WILDERS smoothing relations.
> > > > > > > > > AMA and WILDERS do accept variable periods, like MA.
> > > > > > > > > You will also find some RSI applications there.
> > > > > > > > > Dimitris Tsokakis
> > > > > > > > > --- In amibroker@xxxxxxxxxxxxxxx, "Dave Merrill"
> > > > > <dmerrill@xxxx>
> > > > > > > > > wrote:
> > > > > > > > > > thanks, much appreciated. seems like there's a new
> > > version
> > > > > just
> > > > > > > > out
> > > > > > > > > too (:-)
> > > > > > > > > >
> > > > > > > > > > any chance of variable period RSI, CCI, ROC and the
> > > rest of
> > > > > the
> > > > > > > AB
> > > > > > > > > > indicators I'm forgetting right now? some of these
> I've
> > > > > coded
> > > > > > > up
> > > > > > > > > myself in
> > > > > > > > > > AFL, but they're much slower than the built in
> > > versions.
> > > > > I'd
> > > > > > > > > imagine your
> > > > > > > > > > dll would be pretty close to built in speed, yes?
> > > > > > > > > >
> > > > > > > > > > dave
> > > > > > > > > > In Indicators.dll varperiod Indicators are
> > > > > > > > > > Stochastic
> > > > > > > > > > GraphXSpace=1;
> > > > > > > > > > Plot(StochK(9,1),"",colorBlue,1);
> > > > > > > > > > Plot(scStoch(9),"",colorGreen,1+8);
> > > > > > > > > > Plot(scStoch(RSI(14)),"",colorRed,1);
> > > > > > > > > >
> > > > > > > > > > Ema
> > > > > > > > > > Plot(EMA(C,21),"",colorBlue,1);
> > > > > > > > > > Plot(scEMA(C,21),"",colorGreen,1+8);
> > > > > > > > > > Plot(scEMA(C,RSI(14)),"",colorRed,1);
> > > > > > > > > > Plot(C,"",1,64);
> > > > > > > > > >
> > > > > > > > > > Linregslope
> > > > > > > > > > Plot(LinRegSlope(C,21),"",colorBlue,1);
> > > > > > > > > > Plot(scLinRegSlope(C,21),"",colorGreen,1+8);
> > > > > > > > > > Plot(scLinRegSlope(C,RSI(14)),"",colorRed,1);
> > > > > > > > > >
> > > > > > > > > > MFI // just added today
> > > > > > > > > > Plot(MFI(21),"",colorBlue,1);
> > > > > > > > > > Plot(scMFI(21),"",colorGreen,1+8);
> > > > > > > > > > Plot(scMFI(RSI(14)),"",colorRed,1);
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > > thanks stephane, I'll take a look. until I do,
> can
> > > you
> > > > > tell
> > > > > > > > me
> > > > > > > > > if
> > > > > > > > > > it also
> > > > > > > > > > > contains variable period versions of other
> built in
> > > AB
> > > > > > > > > indicators?
> > > > > > > > > > other
> > > > > > > > > > > than allowing variable periods, do they perform
> the
> > > > > same as
> > > > > > > > the
> > > > > > > > > > native
> > > > > > > > > > > versions? if so, that'd be a nice workaround
> until
> > > > > variable
> > > > > > > > > periods
> > > > > > > > > > are a
> > > > > > > > > > > native AB capability for everything.
> > > > > > > > > > >
> > > > > > > > > > > dave
> > > > > > > > > > > if you want, in indicators.dll there is a Ema
> > > with
> > > > > > > variable
> > > > > > > > > period
> > > > > > > > > > >
> > > > > > > > > > > Plot(scEMA(C,RSI(14)),"",colorRed,1);
> > > > > > > > > > > Plot(C,"",1,64);
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > stephane
> > > > > > > > > >
> > > > > > > > > >
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