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- - One For Barny (http://forums.ozmium.com.au/showthread.php?t=25670)

wesmip1 posted a good way to check the results of a system by luck or edge.

Its a good way to souce out the good from the bad filters in your system.

Quote:

Originally Posted by evajb001

Barny, I don't think mattio is saying his aren't backfitted at all, he's saying the following:

If you have a bunch of data that your backtesting on that goes back say 5 years. You've added in some rules, such as the following:

Days Last Start - between (and inclusive) 5-24
Win Strike Rate - above 24.635%
Placing last start - 1
Placing 2nd last start - 5
Won at track 3 times
Won at distance 3 times

^^ Clearly the above is backfitting, your changing numbers to specifics to maximise your POT, which is great to show a high POT but the chance of that perfect storm repeating in the next 5 years is minimal at best.

Mattio (i think) is simply saying that your aim should be to have logical filters that aren't specified down to minute detail so that you avoid substantial backfitting. So in reference to the above example your filters may be this instead:

Days Last Start - between (and inclusive) 7-21 (logical as its ran on the same day previously, i.e. not starting on a saturday now and some random weekday previously)
Win Strike Rate - above 25% (obvious one, you can't backfit to a specific % its just illogical)
Placing last start - 1 (fine to leave as 1 if you want a last start winner, nothing wrong with this filter)
Placing 2nd last start - 3-x (instead of specifying it had to have finished 5th last start, it needs to be a range otherwise its again being too specific to your backfitting)
Won at track 3 times (you could possibly use this filter but i'd suggest saying won more then 3 times at track, as saying exactly 3 times is too specific again)
Won at distance 3 times (you could possibly use this filter but i'd suggest saying won more then 3 times at distance, as saying exactly 3 times is too specific again)

I think there is room to have maybe 1 filter that is more specific that gives you the edge, but as soon as you start tinkering took much its just over-backfitting too your data. I think thats all mattio is trying to get at Barny, he's not having a shot at you and neither am I, were just suggesting people are careful with how they approach creating a system.

Mate that is the general jist of what I was getting at, thanks for your support. Unfortunately there are people that always have to believe they know exactly what other people are thinking so that will be all I have to say on this topic - hopefully the information will be found to be useful by someone.

Quote:

Originally Posted by Barny

The better divvis come from going against the crowd and the worse ones from following "won at track", "won at distance" ..... everyone is on those filters, have been for ages and will continue to do so. All that does is give you an overbet horse, no matter what other filters you put in.

Hi Barny,

some nice stuff in your post, however I received some 'terrible' divvies on the weekend from track and distance winners, $12 and $23 respectively.

Not all are overbet.

Quote:

Originally Posted by TheSchmile

Hi Barny,

some nice stuff in your post, however I received some 'terrible' divvies on the weekend from track and distance winners, $12 and $23 respectively.

Not all are overbet.

Barny - if you run every race on your database over the 12 years would get a loss of around 15%? not sure of the exact figure

Then using one filter of Won at Distance what is your LOT?
If its better than the result above would it mean you have an edge or is it still overbet?

Quote:

Originally Posted by TheSchmile

Hi Barny,

some nice stuff in your post, however I received some 'terrible' divvies on the weekend from track and distance winners, $12 and $23 respectively.

Not all are overbet.

TheSchmile

"How do you know your $12 and $23 winners represented their true odds and were not overbet?"

.... semantics aside, you know what I'm getting at.

Barny, I can't find anywhere in mattio's posts that he knocked your $4-$30 filter and personally I agree that its a fine filter. It's generalised backfitting with that filter, its not specific. What me and mattio are getting at is that it would be a less enticing filter if it was $4.75 - $29.56 because you'd backfitted it that way to increase the POT.

Your filters that you've mentioned in your post seem fine Barny, as myself and mattio were both saying (in the general sense) that filters shouldn't be specific down to decimils to increase POT, round numbers or ranges instead of specifics will mean your not backfitting too closely to something that is unlikely to repeat or at least repeat anytime soon.

Anyway I feel like my posts are going around in circles now so that enough from me.

Quote:

Originally Posted by Barny

TheSchmile

"How do you know your $12 and $23 winners represented their true odds and were not overbet?"

.... semantics aside, you know what I'm getting at.

In short, I'm a genius Barny! ha ha :)

Sorry I do digress, a fair point you make.

On Sunday, I coupled a few 'Barny-type' factors into my minimum acceptable price. In the race with the $23 winner, the favourite was grossly overbet in my opinion and didn't run a place in a field with <9 runners.

The fav's profile:
It had a win SR of <20% and a place strike rate of <40%, was a sprinter and was running in a low class race.

I completely agree with you that one should look past the obvious when doing the form. If a horse has a 211 formline and opens at $2.50, chances are every mug in Aus will be aboard and the price will often come into unders. If the race is of low standard and the horse shows little sign of further improvement e.g. 5+ runs from a spell, this generally represents a good time to look outside the square and find a horse or two to beat the hotpot.

Quote:

Originally Posted by TheSchmile

I completely agree with you that one should look past the obvious when doing the form...chances are every mug in Aus will be aboard and the price will often come into unders.

BINGO TS! If you want to split from 'the herd' a logical place to start would not be an Open class race on Saturday. "Every mug" and bookie has this race firmly in focus and priced it perfectly. They have it down to a fine art.

Try playing when the mugs aren't concentrating and you can pick the $$$ notes off the floor in relative solitude.