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Howard, thanks for the input. I do have both of your books, btw. And I
am aware of what you state. In 99.9% of cases what you outline is
exactly what should be done.
In my particular system, however, I am not searching for the "best"
value, but rather a range of values that are then looped through in
OOS backtesting to Buy on the best of these conditions that happen to
be "true" at the given bar. These conditions are discontinuous, and
are either completely true or completely false - for e.g. GapUp( ) vs
GapDown( ). Assume that I have, say, three hundred of such different
"states" that I am testing buy/sell conditions against. Each state can
be assigned a variable, and I can optimize to check historical
performance of each state:
optimize ("a", 1, 1, 300, 1);
This type of optimization must be exhaustive, as opposed to using CMAE
non exhaustive, as each state has nothing to do with it's "neighbor"
state. In actuality they are more complex states than simply GapUp or
GapDown. Each state was arrived at by calculations from another
program, and the order that they are tested in the optimization is
somewhat random. Each one is truly unique.
My AFL does the above optimization, and as it does so, I fput the top
50 or so values of "a", according to some custom metric, to an
external file. When it comes time to backtest on OOS data, I then want
to pull those top 50 values and then test to see which "states" are
true (more than 1 can be true), and then Buy on the state that has the
best corresponding metric.
Naturally I can do all of the above manually - e.g. run an
optimization on an IS period using the 'PUSH AFL', then run a backtest
on an OOS period using the 'PULL AFL', and repeat.... But I would
prefer to use the Walk-Forward engine to do all this automatically
and, preferably, with a single PUSH/PULL AFL.
Hope that paints a clearer picture.
--- In amibroker@xxxxxxxxxxxxxxx, "Howard B" <howardbandy@xxx> wrote:
>
> Hi OAM --
>
> The purpose of walk forward testing is to see what happens in the
> out-of-sample period after a trading has been chosen based on
performance
> over an in-sample period. In walk forward processing, you (the system
> designer) do not have an opportunity to evaluate any of the alternative
> systems that are associated with parameter sets other than the one
that is
> at the top of the ranking according to your objective function. The
purpose
> of the objective function is to incorporate everything that is
important and
> arrive at a single-valued score.
>
> So, the question is -- what happens during selection of the best of the
> alternatives based on the in-sample period that tells you to change
> something (use a different system) in the out-of-sample period? If
you have
> a quantifiable answer to that question, incorporate whatever
decision making
> you would do into the original objective function and run the tests
in the
> normal manner.
>
> Or am I missing something?
>
> Thanks,
> Howard
> www.blueowlpress.com
>
>
>
> On Wed, Jan 14, 2009 at 1:57 PM, ozzyapeman <zoopfree@xxx> wrote:
>
> > Hello, I am trying to branch my code whenever the Walk-Forward
engine
> > is processing OOS data. Hoping someone can give me a tip on this.
> >
> > Normally, when one does a Walk-Forward test, the trading system being
> > tested should be identical for both in-sample (IS) and out-of-sample
> > (OOS) data. But there are some rare instances when one might want to
> > use a slightly modified version of the main trading system for the OOS
> > data. Without going into details on my trading system, assume for the
> > moment that the reason for doing such a thing is valid. On that basis,
> > what I essentially want to achieve in my AFL is something like:
> >
> > if ( Walk-Forward engine is processing IS data)
> >
> > { Use Trading System A }
> >
> > if ( Walk-Forward engine is processing OOS data)
> >
> > { Use Trading System B }
> >
> > However, using traces with ActionEx status, indicates that the engine
> > state for both of the above cases is always
"actionExOptimizeBacktest".
> >
> > As such, there is no way (that I can think of) to effectuate the above
> > branching code.
> >
> > Is there a way around this? Some alternate way of testing when OOS
> > data is being processed vs IS data? Or is the only practical solution
> > to build a custom version of the Walk-Forward process using OLE with
> > the AA objects?
> >
> > Thank you for any input.
> >
> >
> >
>
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