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[amibroker] Re: On Robustness, Post #1



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Why do the parameter values HAVE to be the same for all market types?

Parameter values have to fall within a same range of values (min & 
max, for eg., 0 to 17% for sell and 0 to 28% for buy - buy eagerly, 
sell reluctantly) for all markets, regardless of size or nature...  I 
don't need to do optimization for that, else you are curve-fitting.  
How did I arrive at these parameters?  Walk-forward testing...The 
idea is to search for a signal within those range of values...

rgds, Pal

--- In amibroker@xxxxxxxxxxxxxxx, "Al Venosa" <advenosa@xxxx> wrote:
> Test *unoptimized* system on small, mid & large cap stocks in bull, 
bear & sideways market conditions, same parameters for all.  
> 
> Mark: I agree up to a point. However, I'm not convinced that a 
system must perform equally well across all markets using the same 
parameter values, as you suggest. For example, if your system 
performs admirably on the large cap stocks but not on the small cap 
stocks, and within the large cap group the parameter values are 
robust in and of themselves (i.e., no local maxima on the response 
surface diagram), why not trade the system on large cap stocks? Also, 
if you optimize the same system on small cap stocks and find the 
parameter values are different from the large cap parameters but are 
robust, why not use those different parameters for the small cap 
issues? Why do the parameter values HAVE to be the same for all 
market types?
> 
> I use the stocks of the S&P 600, 400, and 500 indices and 2 year 
bull, bear and sideways periods (for a total of 6 years per stock). 
Rationale behind this: to find systems that profitably *tested out in 
the past* on a large number of (somewhat tradeable) stocks of varying 
market caps in multiple sectors under different market conditions, 
under the assumption that this indicates the system is robust enough 
to profitably *trade select issues in the future*. 
> 
> What I like to do is optimize over a period that encompasses BOTH 
bullish AND bearish periods at the same time, like 1/2/99 to 12/31/01 
or 02 as opposed to selecting separate 2-year bullish and 2-year 
bearish periods. Usually, systems have a short component and a long 
component to them (unless you only like to trade either long or short 
per se). So, optimizing the parameters in a trading period that 
includes both bull and bear market action lends a certain degree of 
robustness in and of itself if you find a reasonably flat response 
surface. Then, when you test in the succeeding OOS period and get a 
reasonable performance similar to the IS period, with no local maxima 
in the 3-D space of the trading diagram, then you have a fairly 
robust system in my mind. 
> 
> ...My commission setting(s) in AB: proprietary, based on my 
*slippage* research using data from actual trades.  But you could 
choose an arbitrary say, 1% to get started.  
> 
> What about setting 0 commissions just for starters when developing 
your system. After you have done sufficient optimizing and forward 
testing, then set your commissions/slippage to your 1% or 0.5% or 
whatever and then see if the system crashes. If it does, trash it. 
> 
> Looking forward to your remaining 8 posts. 
> 
> Al Venosa
> 
> 
> 
> 
> ---
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