True odds calculation

[gazuty]

There is probably a very good example of what our friend wants to do coming up.

At present the Djoker is about 2.3 for the Australian open. If he doesn’t show up and pulls out the 43% of the book he currently constitutes will need to be distributed to the rest of the field. Clearly this won’t be equally distributed. Will it be by power law? I don’t think so.

[napshnap]

There is probably a very good example of what our friend wants to do coming up.

At present the Djoker is about 2.3 for the Australian open. If he doesn’t show up and pulls out the 43% of the book he currently constitutes will need to be distributed to the rest of the field. Clearly this won’t be equally distributed. Will it be by power law? I don’t think so.

More likely Djokers released "share" will be proportionally (not equally) distributed among the rest according to their current (before the withdrawal) "share" (so the 2nd strong fav will get a relatively bigger cut of it than others).

[firlandsfarm]

Good post.

I always look to simplify things where possible.

My view on producing a rating for each runner is based on my own experience(s) reading books/forums, testing my own data...etc This doesn't mean I've solved it, because horse racing is an imperfect sport where there is always an incomplete picture.

My approach is to take a set of attributes that I think affect/influence an outcome of a race, weight them and produce a rating. In some cases, combine certain attributes that strengthen the overall rating.

The one thing I found was that the top-rated was often the favourite and well backed. So this told me that the market makers seemed to be taking into account similar information into their algo. I also quickly learned, that sometimes, the bottom rated would win, but the price was a value one comparing the market price with my own tissue price. I also learned that if a favourite was poorly rated, they ran poorly too.

Taking all that into account, there are many ways I can utilise one set of ratings. This includes In-Play if the race is going the way I visualised it.

I also tend to avoid tweaking things as horses aren't machines and will have off days, be unlucky, or the jockey might make a mistake.

My early attempts were shite, but I learned from them. I also believe there are websites/resources that present the information better and would save a lot of time, but I enjoy the process.

Hi foxy, yes ... there are two stages, first gather and process your data and then second convert that data into odds. It's the second stage that I am seeking the holy grail for. All runners can win ... there has been 7 winners at BSP odds of 1,000! Your approach above is fine but I don't think you are describing a calculation of ratings to odds, it's more an opinion. I (think) I remember seeing a spreadsheet from you on the forum (and please accept my apologies if I'm wrong) where you basically apportioned each runner's rating against the sum of the ratings and used that as a form of probability. And that may well have worked and if it does, great, keep going but maybe it has benefitted from variance being in your favour as Peter explains in one of his videos. That method is covered on some punter websites but I don't see it as standing up to mathematical theory. And that's why I am still looking.

[firlandsfarm]

Alright, I maybe misread it, it sounded like you can't calc (convert) odds from ratings, weights or other metrics at all.
I agree that you can't calc "true odds" (cause "true odds" is a controversial entity).

No I don't think you misread that bit. there are many stabs at converting ratings to odds I just don't see them able to stand up to mathematical theory. By calculating I mean put a set of ratings into a spreadsheet and have it calculate the respective odds with no interaction with the user.

...

So, if this (viewtopic.php?p=275183#p275183) doesnt fit your desire then I give up).
ps. AFAIR I overcomplicated it a lil bit and there is much simpler method in that thread.

I'm afraid you are going to have to give up napshnap! That's the system that to me has no mathematical foundation. Why should adjusting your ratings by a random factor into an artificial structure and then pro-rata them give a reliable probability? Take a two runner race and give one runner a rating of 100 and the other a rating of 50. Using the sum and proportion approach would give odds of 1.50 and 3.00 respectively but I doubt you would find a bookmaker who would give you 1.50 on the favourite with such an ability advantage. I note that some contributors to that thread and the FlatStats thread referred to take a similar view as me.

The problem is being able to convert the odds compiler's judgement into an algorithm capable of being calculated. The human brain can think and reason, computers cannot until the analysts can tell the coders exactly how we think about and reason things in every combination of variables.

[wearthefoxhat]

Good post.

I always look to simplify things where possible.

My view on producing a rating for each runner is based on my own experience(s) reading books/forums, testing my own data...etc This doesn't mean I've solved it, because horse racing is an imperfect sport where there is always an incomplete picture.

My approach is to take a set of attributes that I think affect/influence an outcome of a race, weight them and produce a rating. In some cases, combine certain attributes that strengthen the overall rating.

The one thing I found was that the top-rated was often the favourite and well backed. So this told me that the market makers seemed to be taking into account similar information into their algo. I also quickly learned, that sometimes, the bottom rated would win, but the price was a value one comparing the market price with my own tissue price. I also learned that if a favourite was poorly rated, they ran poorly too.

Taking all that into account, there are many ways I can utilise one set of ratings. This includes In-Play if the race is going the way I visualised it.

I also tend to avoid tweaking things as horses aren't machines and will have off days, be unlucky, or the jockey might make a mistake.

My early attempts were shite, but I learned from them. I also believe there are websites/resources that present the information better and would save a lot of time, but I enjoy the process.

Hi foxy, yes ... there are two stages, first gather and process your data and then second convert that data into odds. It's the second stage that I am seeking the holy grail for. All runners can win ... there has been 7 winners at BSP odds of 1,000! Your approach above is fine but I don't think you are describing a calculation of ratings to odds, it's more an opinion. I (think) I remember seeing a spreadsheet from you on the forum (and please accept my apologies if I'm wrong) where you basically apportioned each runner's rating against the sum of the ratings and used that as a form of probability. And that may well have worked and if it does, great, keep going but maybe it has benefitted from variance being in your favour as Peter explains in one of his videos. That method is covered on some punter websites but I don't see it as standing up to mathematical theory. And that's why I am still looking.

Yep, fair enough.

The only thing I can add is;

1. Convert the rating to a base odds figure. (standard stuff)
2. Compress the top 4 (could divide by 2)
3. Spread the remaining 100% book (add and overround) with remaining runners.
4. Compare current market price / your tissue price (Any figure >1.00 is on the value short list, the higher the better)

Value betting/laying can be frustrating, but equally rewarding when it clicks into place.

[Archery1969]

This was very good value.

[goat68]

This was very good value.

Presumably trap 3 also good value?

[ShaunWhite]

This was very good value.

Presumably trap 3 also good value?

I don't understand that value col, they're all +ve. And the best value of the lot would be laying trap 2 ?

[goat68]

This was very good value.

Presumably trap 3 also good value?

I don't understand that value col, they're all +ve. And the best value of the lot would be laying trap 2 ?

I read it as the higher the "value" number rating the better value it is...?

[goat68]

This was very good value.

Presumably trap 3 also good value?

I don't understand that value col, they're all +ve. And the best value of the lot would be laying trap 2 ?

Looks like it is Betfair Odds/Calc(tissue) odds

[goat68]

So "back" value!

[wearthefoxhat]

Arch.png

That's the process for sure

I'd be tempted to Lay the slower starting T5 @ 3.25 in that one.

Sometimes keeping it simple is all that's needed.

[napshnap]

No I don't think you misread that bit. there are many stabs at converting ratings to odds I just don't see them able to stand up to mathematical theory. By calculating I mean put a set of ratings into a spreadsheet and have it calculate the respective odds with no interaction with the user.

...

So, if this (viewtopic.php?p=275183#p275183) doesnt fit your desire then I give up).
ps. AFAIR I overcomplicated it a lil bit and there is much simpler method in that thread.

I'm afraid you are going to have to give up napshnap! That's the system that to me has no mathematical foundation. Why should adjusting your ratings by a random factor into an artificial structure and then pro-rata them give a reliable probability? Take a two runner race and give one runner a rating of 100 and the other a rating of 50. Using the sum and proportion approach would give odds of 1.50 and 3.00 respectively but I doubt you would find a bookmaker who would give you 1.50 on the favourite with such an ability advantage. I note that some contributors to that thread and the FlatStats thread referred to take a similar view as me.

The problem is being able to convert the odds compiler's judgement into an algorithm capable of being calculated. The human brain can think and reason, computers cannot until the analysts can tell the coders exactly how we think about and reason things in every combination of variables.

"Using the sum and proportion approach..." It's a kinda primitive way to calc odds.If you'll try the method described in my link with a user defined parameters 10 and 90 you'll get 1,1 and 10. If you really hate any user involvement in calculation you can that try another approach: using excel use STANDARDIZE on rating and then use NORMSDIST than calc odds from numbers you got. It gives 1,2 and 6,3.
Closer to imaginable bookie prices innit?

[ShaunWhite]

Looks like it is Betfair Odds/Calc(tissue) odds

If so that's skewed with small or large numbers, better to compare implied chance precentages. Tbh I never use odds in any calcs, its always percentages to keep the maths clean and simple and consistent over the whole ladder.

[Archery1969]

There are a number of ways of doing it. In my example if Value < 1 then look to lay or > 1 then look to back.

For backing then use the highest number and for laying use the lowest.

Odds are always based on opinion, although in that race allot of people seem to get it wrong as the favourites sectional times were not great.