Maths help

[Mitch]

If I make several trades on a market on different selections so that I have different amounts of green on each selection, is there a mathematical way of deciding what bets to make to make all selections equal profit?

Thanks for any help.

[GeorgeUK]

Mitch - looked at this a while ago, but gave up and tried writing a macro to keep laying half of the largest profit, then it got down to pennies out.

Had another look and i must have screwed something up - because it works out...

No it doesn't - muppet moment - sorry



OK - time for another laugh (my calculation attempts)
The amount to stake on each selection:

Average of total profit/loss - that selection's profit/loss / the selections odds.


And i know what you're thinking - it's not just the selections that are odd...

[Mitch]

Thanks George, I'll give it a go and let you know how it goes.

This is the way I first thought of trying it but then I thought - as soon as 1 bet is placed it changes the P/L on all the other selections, then when you change the next one it changes all the others including the first one - then my head started to hurt and decided to post on here

I'm going to give it a go now.....

[Uncle Ernie]

mitch the calculations aren't that complicated as you have all the figures to hand i.e. profit and loss and odds/ available and available stake just from the profit/loss column. Just consider how you calculate an overround book at present and set it to calculate an even profit using selections that are negative, you'll find the calcs actually balance themselves from the figures you give them to work from

[Mitch]

Ernie, I'm glad that it's possible, and more than that - not too difficult.

I have a friend (ahem ) that although fairly bright is not used to calculating such figures and would appreciate any elaboration on your above post, especially an example.

Thanks again.

[GeorgeUK]

Mitch - while waiting on Ernie's reply - here's another stab in the dark.
My last attempt was tring to back a negative value on some selections!!!
(I promise - it was the medication )

How about this

1 / selection_odds * (max_profit - Selection_P/L)

just for a giggle

[Mitch]

Dunno George.

The one way I tried it fails when you only have a value other than 0 on 1 selection. If you don't include the zeros in the average calculation, the profit on the 1 selection the same as the average so you end up with a stake of 0, and then an error.

If you calculate the avergae with the 0's included then you must have to place a bet on every selection wether you've traded on it or not, which could lead to very poor value just for the sake of levelling up.

My head still hurts

[Uncle Ernie]

Mitch, imagine we're laying to get an overall profit.

You look at the highest loss you have say -50

So we call a cell "minimum" and log the figure in that cell - We now aim to get all our runners on the same loss -50. So if that profit and loss is showing 44 we aim to get a 94 loss by laying that runner at say 12 for 7.83. Do the same calc for all the selections then add up the the amount you'd need to stake-if thats over the max loss then you're in the money if not either take the loss or wait.

The pic below may make more sense but I'm sure you get the idea

http://img399.imageshack.us/img399/1432 ... ed3zr1.jpg

The figures in V5 and W5 would read 0.00 & 0.00 for Fear the cape I deleted them by mistake.

[Mitch]

The penny drops thank you Ernie.

[Uncle Ernie]

No problem, obviously to balance by backing it's just a point of turning it round and treating the difference between max and minimum from the profit/loss column as your book to back to.

It's worth having your sheet doing both backing and laying calcs to see which is the most profitable. The closest to 100% either back or lay would give the best returns but you also need to consider how many bets you're kicking off - If you've laid 3 runners in a 20 runner race it much better to back those 3 to get your balanced book than lay the other 17 runners as some may not get matched.

Depends on you're betting strategy if you balance by backing or laying but the calcs are basically quite simple either way.

[tkp]

Thanks U.E.

Could you explain which selection(s) we would lay in your example - is it runner 1 or all the others ? My brain hurts now (luckily there isn't much to hurt!).

Thanks,

tkp

[GeorgeUK]

You would be laying all the other selections tkp.

eg No.3 Shift gears - you would be laying for 7.83 @ 12 odds (giving the liability of 94)

the selection with the lowest profit (Fear the Cape) would not have any lay bets made on it.

[tkp]

Cheers George.

[tkp]

I've figured out the lay side of things thanks to U.E. and George.

Any chance someone can explain how to do with this by Backing ?

Cheers,

tkp

[GeorgeUK]

As per my previous post

1 / selection_odds * (max_profit - Selection_P/L)


Ernie does it slightly differently.

(max_profit - Selection_P/L)/selection odds


Same thing really, but just thought i'd show what Ernie came up with.