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- 13 June 2007
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Hello Howard. Substance? Evidence in the form of results or more to the point, evidence in the form of trading algorithms or methods.
Hi David --
There is a "theorem" of machine learning that is called "no free lunch." It states, loosely, that it is not possible to know which model is best for a given problem in advance of running the fit and test processes.
Random forest is one of several "ensemble" techniques that use many (often thousands) of relatively simple but, importantly, dissimilar models, each of which is a "weak learner" to combine into a more powerful learner. Ensemble techniques do well in many applications.
Each individual tree is predicting the same target. (More below) Individually, they may be identifying different patterns, but then together they are predicting the same target.
The logic used to decide how individual trees will be included depends on the ensemble algorithm used -- the individual trees may be equally weighted or the weight may depend on the accuracy.
The modeler (that is the person building the model) chooses what the target to be modeled is. A common target is the relation between today's close and tomorrow's close. There are two broad model categories -- classification and regression.
For a classification problem, the classification categories are binary -- for example "long" or "flat." For a regression problem, the target is a more-or-less continuous numeric value -- for example the percentage change from today's close to tomorrow's close. In the vocabulary of traditional analysis, this is the dependent variable.
The predictor variables (independent variables) can be anything. To be useful, they should change in some identifiable way at about the same frequency as the target changes. Technical indicators with short lookback periods work -- RSI(2), for example. Pick one -- multiple fast oscillating technical indicators are redundant and usually reduce the accuracy. Raw price is almost never used. Formulation of predictor variables is one of the major tasks of the modeler.
Nodes? What are you thinking of when you say node?
Ensemble models are made up of "simpler" models. Pruned decision trees are often used because they are fast to create and train, and they have high variance. Conceivably, neural networks could be used. Calculation time could be a problem. Try it to see. Think through when, relative to placing the trading order, the models will be trained and how they will be recalled for prediction.
Best regards, Howard
Howard,
when i mentioned node, i meant the branch on a tree, or decision point. Hence if a formula such as c<ma(c,5) is true then go left otherwise go right. Building such a tree would be relatively simple, is that what you should use, or is there something better.
I could actually see this working a lot better on fundamental data rather than price action.
Thanks,
Hi Howard,
What would you recommend as a starting guide/ actions/resources for someone beginning their Quant journey?
cheers
Hi Omega --
For free, begin by watching these videos:
http://www.blueowlpress.com/video-presentations
The very first book to read is Daniel Kahneman's "Thinking, Fast and Slow."
https://www.amazon.com/Thinking-Fast-Slow-Daniel-Kahneman/dp/0374533555/
Of my books, "Quantitative Technical Analysis."
http://www.blueowlpress.com/123-2/quantitative-technical-analysis
Best regards, Howard
Morgan will not build those departments and pay those costs unless the trading results are adequate to fund them.
Hi Howard,
So what returns are these companies making, on average, vs the market index? Because I have often read that the vast majority of fund managers fail to beat the market index. Is that correct, or am I way off the mark there?
I've read the top ones are consistently in the 20-30%pa range. Pretty good for their size I guess.
http://www.barrons.com/articles/best-100-hedge-funds-1466223924?tesla=y
when a strategy of just buying and holding the index would produce more or less the same returns.
It's only a 3 year annual return shown, so not really representative of their typical returns, but even so it shows that these very top 100 hedge funds returned an average of 16.98% vs 15.13% for the S&P500. I'd say that if you looked at their 10 year performance the difference would be far less. I just came across an article stating "The 20-Year Performance Of Hedge Funds And The S&P 500 Are Almost Identical". So if that is right, you would have to wonder why these companies would spend vast amounts of money employing all these quants, when a strategy of just buying and holding the index would produce more or less the same returns.
Managing Millions or Billions year on year to a profit is a vastly different and more difficult task than doing the same as a single retail investor.
Exactly! However Howard is painting this picture that these companies are going to totally destroy us retail traders, due to all their resources and talented people that they employ. But I don’t see any evidence of that in these results. These funds are at a severe disadvantage to us retail traders due to their size. Perhaps Howard can show us some evidence to support his claim.
I don’t see these big trading companies as being our competition anyway. Due to their size, they are playing at a completely different ballgame to what we are playing.
And as for simple systems not working anymore – well you can’t get any simpler than buy-and-hold a low cost index fund, but this approach will, apparently, beat the majority of professional fund managers.
Exactly! However Howard is painting this picture that these companies are going to totally destroy us retail traders, due to all their resources and talented people that they employ. But I don’t see any evidence of that in these results. These funds are at a severe disadvantage to us retail traders due to their size. Perhaps Howard can show us some evidence to support his claim.
I don’t see these big trading companies as being our competition anyway. Due to their size, they are playing at a completely different ballgame to what we are playing.
And as for simple systems not working anymore – well you can’t get any simpler than buy-and-hold a low cost index fund, but this approach will, apparently, beat the majority of professional fund managers.
I don't think he is making that claim at all.
If you're really bright and can program at a high level, why on earth would you work for a hedge fund where other people are getting wealthy on the back of your hard work... and in the process eroding your edge? You'd maybe work for them for a while, keep your best work to yourself until you save up and then go solo.
The only time it would make sense to use someone else's money is if you're a good discretionary trader, and even then, the moment you succeed, everyone is going to be watching your every move.
What I'm saying is, the big funds aren't set up to be able to find the best ideas. People know what ideas are worth and they don't want to have their IP used unless they are paid extremely well.
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