Cross-Matching

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

so the best back prices would resolve as 1.76 , 2.5 & 6


i.e.  for the Newcastle price the calc would be  =1/(1-(1/3+1/10))

Chelsea = 1/(1-(1/2+1/10))

The stakes would be set by the smallest payout available from those 3 prices

You are a star Baby Jesus - thanks very much!

Anyone know if there is no cross matching on the fa trophy in the football?

The home and away lay prices are 1.73 and 5.9 butthe best price available on the draw is 3.85...

Surely it should be 3.95?

=1/(1-((1/1.73)+1/5.9)) = 3.96 i.e. rounded down to 3.95??

There probably wasn't enough money backing at 1.73 for the minimum stake to be displayed on site. Remember the liability is split equally over the other outcomes so for £2 to be displayed at 3.95 they'd need to be at least £4+ backing at 1.73. It's switched on for most  football markets

Ah right I see, thanks again pal.

ok so now I'm trying to get my head around the liability thing. In the betfair example there £120 quid at 2.0 to lay on newcastle, £150 at 3.0 to lay on chelsea and apparently this equates to £40 on our new best draw at 6.0?

Can you help me understand how this works please? I can see where £120 comes from but how do you work out the inverse of £150 at 3.0? And how do you then arrive at £40, is it just £120-£80?

So confusing for my little brain :S

Think of it as if you were laying or making a balanced 100% book

We have £120 at 2 which gives us a £240 payout
£150 at 3 gives us a £450 payout

For cross matching we need to balance those amounts equally or we'd have an unbalanced book so we need to use the lowest payout of £240, because that can be spread over all outcomes we can also lay a payout of £240 from the £450 on Chelsea. This now gives us a maximum payout we can do of £480, we simply divide this by the odds so £480 divided by 6 = £40.

So the overall payout is always going to be set by to lowest figure but because that's also spread across the remaining runners we can muliply it by however many other outcomes we're using to set the x matched odds.

Oops cocked that up a bit,

This now gives us a maximum payout we can do of £240, we simply divide this by the odds so £240 divided by 6 = £40.

Ignore the "So the overall payout is always going to be set by to lowest figure but because that's also spread across the remaining runners we can muliply it by however many other outcomes we're using to set the x matched odds."

Thanks for responding, I really appreciate it. The help on here is much better than on te API forum.

Ah so we need to find the loewst amount matched on the other selcetions and times by the lay odds on this and then divide by our new back odds?

So the £80 on Chelsea comes from £240/3.0 and we use this £80 and the £120 on Newcastle to pay us out the £200 (£40 at 6.0) on draw??

Think I get it! Cheers

Yes that's correct, the remaining £70 @ 3 (£150-£80) on chelsea is now used with the next available bet on newcastle £75 @ 2.5 to create another virtual bet of 3.75 for £50 on the draw.

Again the minimum payout is set by the smallest amount

£75 x 2.5 = £187.50 Newcastle
£70 x 3 = £210.00  Chelsea ~~~~(we only need a stake of £187.50/3 = £62.50 to create that balanced book )

so £187.50 divided by the 3.75 gives us £50

the payout of £50 @ 3.75 ( £137.50) would come from £75 newcastle and £62.50 chelsea.

In Betfairs example we still have £7.50 available on Chelsea at 3, this would be used to create another virtual bet with the next price on Newcastle which was 1000. That price wouldn't be displayed because it is worse than the current 3 price boxes.

Perfect! Exactly how I understand it now and I've got my code displaying everything as on website - thanks again for your help!