Betfair cross matching explained!

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PeterLe
Posts: 3715
Joined: Wed Apr 15, 2009 3:19 pm

Yes I agree..
Also for anyone using automated strategies; you can see how things (EG WOM) is shown differently depending upon whether you have it switched on of off.. so could help or hinder a strategy..
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LeTiss
Posts: 5386
Joined: Fri May 08, 2009 6:04 pm

PeterLe wrote:Yes I agree..
Also for anyone using automated strategies; you can see how things (EG WOM) is shown differently depending upon whether you have it switched on of off.. so could help or hinder a strategy..
Yeah, that's a great point actually

I've come to realise over the years that WOM is quite often a trap, as much as a guide.
vhdgkl
Posts: 63
Joined: Thu Feb 25, 2016 9:26 am

PeterLe wrote:Cross matching was introduced on the 24th Nov 2010 (?) and I remember the build up wondering what would happen (there is a tread on here somewhere)
This explains what it is and is the best explanation Ive seen:-

https://api.developer.betfair.com/servi ... rtual+Bets

Although its a straight forward calcualtion; it seems to behave differently these days that when introduced originally.

Here is a video I did at the time (Pause the video as it plays and you can compare the subtle differencesin odds/money avail at those odds between one account with Cross Matching and one account with no cross matching)

https://www.youtube.com/watch?v=3njy483sL-w

Once you understand how it works; you will drive yourself mad trying to work out how to exploit it! :D
https://www.youtube.com/watch?v=3njy483sL-w

i saw this link

it's really hard to understand formula..and it's really really hard to undersand why in a moment(13seconds)the lay odds of third is different(4,1no xm-4,2 whit xm :o )
the book percentage is 101.5 for the lay column in that moment(and backers column is under 100percentage!), why the odds up?

ps:I think the key to understanding why the odds when they take you take you systematically disadvantage 'to look for in this cross-matching (english is not my language :D )
PeterLe
Posts: 3715
Joined: Wed Apr 15, 2009 3:19 pm

Folks,
Pre API-NG, Betfair had a doc that explained the cross matching principle, they had a example based on a football match and accompanying it they had a formula.
Does anyone have a copy of that formula please? (betfair still have examples of cross matching but they seem to have removed the formula)
I know betfair cross match against linked markets, I know that, but Im just looking for that original formula, if anyone can help
Thanks in advance
regards
Peter
spreadbetting
Posts: 3140
Joined: Sun Jan 31, 2010 8:06 pm

1 / (N –∑ 1/(best to lay price of other runners))

Where N is the number of winners that market will have, e.g. for a “to win” market N = 1, for a place market with 3 winners N = 3.

For each runner calculate the available stake at that price as:

MIN(odds1*stake1, odds2*stake2...oddsn*staken) / [the price calculated in step a. above]
In plain English the stake you can match is limited by the payout (odds*stake) available on each of
the component bets that you’d need to match.
Last edited by spreadbetting on Wed Jun 27, 2018 7:17 pm, edited 1 time in total.
PeterLe
Posts: 3715
Joined: Wed Apr 15, 2009 3:19 pm

spreadbetting wrote:
Wed Jun 27, 2018 6:55 pm
1 / (N –∑ 1/(best to lay price of other runners))

As far as I can remember.
Hi
Thanks for the reply; (good memory! :D ) Yes I just found it too...Extract below

For the available to back prices on the LHS:
• For each runner calculate the best price at which you could effectively back that runner by
laying all the others:
1 / (N –∑ 1/(best to lay price of other runners))
Where N is the number of winners that market will have, e.g. for a “to win” market N = 1, for a place
market with 3 winners N = 3.
• For each runner calculate the available stake at that price as:
MIN(odds1*stake1, odds2*stake2…oddsn*staken) / [the price calculated in step a. above]
In plain English the stake you can match is limited by the payout (odds*stake) available on each of
the component bets that you’d need to match.
• Repeat from the first step above

Taken from : http://www.bettingdeveloper.org/docs/Be ... 0Guide.pdf
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