Racehorse TALK
Thoroughbred Racing Talk => Racing Talk => Topic started by: bascoe on 2019Nov01, 02:58 PM

I am looking to save a bit of time in some aspects of my betting.
Using Betfair  I want to make a back bet on a runner, then have my software make an 'appropriate' place back bet on the same runner.
My question is "what odds should I be looking to take for the place based on the taken BF back price?
I know they are separate markets but I was looking to see if I could derive a suitable price based upon the win price.
I know the traditional 1/4 odds for 8 or more runners, 1/5 for less etc but can anyone share their thoughts on this?

Foreach perm a,b,c
p=TrifectaProb(a,b,c)
Place[ a]+=p;
Place[ b]+=p;
Place[ c]+=p;

Always respect your answers jfc and I know the gold is in the ore...
I am wondering though, if a runner price is $4.0 what would be the best place price to take?
keeping it simple like...if you know what I mean

The win price alone isn't enough to calculate the place price.
If you have an 8 horse field and the prices are $1.34  $4.00 and 6 other runners at $1000  your $4.00 chance might be $1.01 to run a place
If you have an 8 horse field and the prices are $4.00 and 7 runners at $9.33 your $4.00 would be $1.70+ to run a place.
If you think the win price is overs  and you are confident the runner won't shorten a lot eg bet late  I'd suggest the easiest option for you would be to take the Betfair Place SP where available on the basis it will be close to the appropriate place price based on the race market.

BSP,BSPP
1.651,1.087
1.732,1.216
1.780,1.080
1.791,1.094
2.002,1.272
2.043,1.230
2.078,1.180
2.300,1.171
2.320,1.285
2.439,1.269
2.441,1.230
2.532,1.234
2.643,1.245
2.812,1.507
2.878,1.368
2.920,1.400
3.106,1.552
3.202,1.264
3.217,1.600
3.218,1.450
3.232,1.510
3.299,1.280
3.341,1.516
3.350,1.740
3.450,1.380
3.450,1.519
3.483,1.656
3.518,1.549
3.568,1.325
3.600,1.626
3.630,1.547
3.670,1.788
3.700,1.601
3.700,1.680
3.700,1.790
3.800,1.815
3.854,1.940
3.894,1.650
3.933,1.614
3.988,1.767
4.000,1.812
4.030,1.710
4.071,1.800
4.100,2.478
4.200,1.670
4.200,1.840
4.200,1.990
4.257,1.772
4.257,1.412
4.275,1.818
4.389,1.706
4.400,1.613
4.400,1.720
4.400,1.772
4.426,1.613
4.434,1.915
4.500,1.837
4.557,1.483
4.684,1.541
4.772,1.846
4.813,2.004
4.822,1.580
4.900,2.518
4.973,2.037
5.000,1.760
5.012,1.591
5.086,2.105
5.093,2.100
5.100,1.942
5.174,2.155
5.195,2.145
5.246,1.820
5.285,2.027
5.400,2.746
5.440,1.979
5.476,1.920
5.500,2.140
5.555,1.740
5.600,2.176
5.634,1.870
5.654,1.741
5.700,2.105
5.800,1.981
5.989,2.077
6.000,1.689
6.014,2.190
6.062,2.109
6.105,2.231
6.106,1.890
6.161,2.412
6.165,1.819
6.197,2.040
6.321,1.714
6.400,2.100
6.400,2.213
6.400,2.402
6.434,2.457
6.600,1.932
6.600,2.260
6.600,2.270
6.676,1.635
6.728,2.148
6.738,2.040
6.918,2.408
6.934,2.387
6.969,2.661
7.000,2.371
7.127,1.681
7.155,2.767
7.160,1.716
7.173,2.340
7.192,2.918
7.200,2.148
7.210,2.220
7.260,2.618
7.296,2.485
7.364,3.400
7.373,2.440
7.465,2.782
7.516,2.280
7.574,2.399
7.666,2.320
7.719,3.428
7.726,2.560
7.770,2.612
7.776,2.640
7.789,2.120
7.800,2.707
7.800,2.770
7.820,2.796
7.874,1.844
7.889,2.231
7.924,2.520
8.000,2.680
8.000,2.760
8.027,2.900
8.032,2.820
8.053,3.750
8.084,2.534
8.108,2.779
8.128,2.852
8.200,2.480
8.200,2.880
8.228,2.922
8.239,2.723
8.325,2.967
8.335,3.570
8.400,3.014
8.400,1.760
8.400,2.647
8.400,2.840
8.424,3.134
8.592,2.640
8.594,2.868
8.600,2.700
8.600,2.808
8.645,2.960
8.800,3.141
8.807,3.654
9.032,2.700
9.047,2.842
9.200,2.612
9.322,2.620
9.346,2.487
9.400,2.980
9.570,3.557
9.629,2.800
9.767,2.961
9.800,2.253
9.921,3.087
9.973,3.397
9.993,2.925
10.000,2.640
10.000,3.050
10.000,4.697
10.085,3.289
10.192,2.867
10.203,3.630
10.285,3.150
10.286,2.740
10.312,3.497
10.500,3.400
10.500,4.700
10.697,3.300
10.919,3.450
11.000,2.345
11.000,2.740
11.000,2.940
11.000,2.981
11.000,3.085
11.000,3.229
11.128,2.868
11.250,3.612
11.393,2.763
11.612,2.160
11.618,2.902
11.689,4.883
11.811,2.700
12.000,3.171
12.000,3.300
12.000,3.550
12.000,5.100
12.000,5.800
12.013,4.013
12.016,4.266
12.164,4.118
12.340,2.600
12.500,3.600
12.517,3.935
12.648,3.753
12.752,4.002
12.847,3.259
12.858,3.735
12.973,4.902
12.990,3.551
13.000,2.556
13.000,2.613
13.000,3.700
13.000,3.911
13.006,3.650
13.180,3.250
13.270,2.636
13.500,2.931
13.500,3.360
13.500,3.681
13.713,4.100
13.739,3.337
14.000,4.000
14.000,4.562
14.016,3.700
14.043,3.600
14.048,3.550
14.175,3.950
14.302,3.596
14.307,4.840
14.500,3.831
14.500,4.125
14.690,3.950
14.769,4.124
15.000,3.700
15.000,3.764
15.000,4.300
15.033,3.924
15.102,4.000
15.500,3.462
15.500,4.400
15.500,4.500
15.751,3.700
15.830,3.650
16.000,3.950
16.000,4.000
16.000,4.200
16.000,4.216
16.133,6.400
16.292,4.962
16.590,5.300
16.623,4.800
16.863,3.588
17.000,3.908
17.000,3.996
17.000,4.000
17.080,5.000
17.098,4.400
17.163,5.482
17.178,4.057
17.289,2.821
17.319,6.197
17.347,3.038
17.500,5.100
17.597,4.100
17.820,3.972
18.000,5.300
18.000,5.700
18.078,2.895
18.299,4.736
18.487,4.769
18.500,3.717
18.500,4.059
18.641,4.400
18.720,4.481
18.821,6.800
18.868,4.500
19.000,2.975
19.333,3.916
19.395,4.500
19.529,4.613
19.692,3.751
19.831,4.541
19.964,4.900
20.000,3.703
20.352,5.026
20.451,5.226
20.649,5.000
20.666,4.100
20.784,5.300
21.000,3.025
21.489,3.515
22.000,3.382
22.000,5.600
22.129,7.475
22.824,5.700
23.000,5.374
23.000,6.229
23.000,6.365
23.000,6.600
23.296,5.250
23.327,5.950
23.387,5.000
23.738,4.911
25.000,4.501
25.000,4.502
25.000,5.500
25.084,3.615
25.375,4.400
25.881,7.000
26.209,3.100
27.000,3.647
27.332,6.000
27.494,4.141
27.519,5.739
27.899,9.640
27.952,4.001
28.000,5.662
28.000,8.200
28.110,5.847
28.504,7.771
29.751,4.618
30.000,6.480
30.000,7.800
30.000,7.420
30.120,12.093
30.183,6.200
30.812,7.687
30.910,6.200
31.414,6.532
32.000,7.751
32.815,7.000
33.087,6.800
33.396,6.523
33.875,7.572
34.000,8.118
34.661,5.114
34.684,9.745
35.364,6.087
35.513,7.800
35.892,5.400
36.000,5.700
36.025,8.000
36.145,8.408
36.245,7.235
36.995,7.413
37.398,7.800
37.451,6.000
37.616,8.296
37.759,7.417
38.000,6.424
38.000,6.800
39.128,7.200
39.357,6.200
40.000,7.400
40.000,8.000
40.071,7.400
40.376,6.000
41.733,5.300
42.000,8.292
42.000,11.220
43.127,7.000
43.272,9.200
43.486,11.994
43.895,9.800
43.912,6.800
44.000,7.600
44.000,7.777
44.233,10.973
45.393,8.000
45.753,7.800
45.844,14.624
46.000,8.600
46.000,11.000
46.213,7.853
46.602,8.200
47.504,9.414
47.849,8.953
48.130,6.773
48.342,12.058
48.379,10.500
50.594,13.001
50.638,9.400
50.837,10.748
53.205,11.000
53.399,8.622
53.501,9.579
55.000,7.600
55.000,10.500
56.750,13.751
57.004,10.000
57.593,9.901
58.827,10.732
59.770,6.400
59.954,6.200
60.000,6.800
60.000,10.000
60.000,11.000
60.000,11.739
60.000,12.500
60.543,7.483
62.643,10.710
62.693,7.800
62.840,14.064
62.930,9.626
62.966,10.297
64.678,8.800
65.000,7.600
65.000,10.500
65.000,13.606
65.208,10.500
71.335,8.927
71.563,11.500
73.092,15.308
73.675,12.500
75.000,7.542
75.000,13.500
79.015,10.500
80.000,12.297
80.000,12.500
80.000,14.475
80.288,22.000
82.663,11.888
85.000,13.081
90.248,13.500
90.770,13.942
91.130,12.341
92.437,12.500
94.007,17.000
96.241,9.247
97.952,21.000
98.235,10.262
100.000,11.000
102.805,10.000
103.436,14.992
104.395,9.000
109.927,21.000
110.000,21.000
113.836,21.000
115.725,14.000
118.693,10.217
119.674,16.763
120.000,15.469
120.994,19.495
124.469,24.000
125.344,17.500
126.057,19.841
128.903,24.000
130.000,17.000
130.000,23.000
130.782,21.312
140.000,11.972
152.612,25.000
154.930,21.000
160.000,24.000
168.409,19.500
170.000,14.008
170.102,23.630
184.313,17.500
190.000,17.500
191.352,30.000
191.370,24.000
193.525,30.535
200.573,25.755
205.682,20.951
210.000,34.000
218.302,29.952
219.789,30.000
222.782,32.000
223.686,44.000
234.294,26.236
240.000,19.969
240.000,33.160
278.982,21.022
292.133,44.000
300.000,47.173
310.000,27.000
438.288,119.044

Luckily there's not much activity today, so the previous post is a comparison of Win to Place BSPs for a few races on October 20.
This may demonstrate that there is no simple relationship between the 2.
Anyone not convinced is welcome to expand the exercise to also order by Field Size.

Thanks for those who responded. Found a great answer on page 51 of Roger Dedman's book 'Commonsense Punting':
"Using a theoretical race of 8 runners (the number is really immaterial as you will see later) with the favourite at $2 and your selection( for a place) at $6 to win.
Assume that evens and $6 are fair prices, so that F(fav) probability of winning is 1/2 (50%) and S (your selection ) probability is 1/6 ( 17%) . Between them they have 50% +17% = 67% = 2/3. So the probability of something else winning is 1/3 (33%).
From here on, the abbreviation PR (X) stands for the probability that the event X happens: e.g. PR (F) stands for the probability that the favourite wins.
If there are six other runners then each of them has a probability of winning of 1/16 ( one sixth of 1/3), assuming them all to have equal chances.
A place bet on S (your selection) will win in the event of any six of ( 6) distinct results:
(a) S wins: PR(S) = 1/6 = .1667
(b) F wins S 2nd PR (FS) = 1/2 x 1/3 = 1/6 = .1667
(c) an outsider wins, S 2nd PR(XS) = 1/3x 16/94 = .0588
(d) F wins S 3rd PR (FXS) = 1/2x2/3x16/44 = .1250
(e) F 2nd S 3rd PR (XFS) = 1/3 x 50/94 x 16/44 = .0662
(f) S 3rd , F unplaced: PR (XXS) = 1/3x 27/94x 16/89 = .0220
TOTAL .6054 These probabilities total .6054 or odds a little shorter than 4/6 so a place dividend equal to or better than $1.65 is acceptable."

Having the market is only the beginning of the puzzle  you need to google favouritelongshot bias and Harville bias and be prepared for a lifetime of interesting analysis.

Thanks for those who responded. Found a great answer on page 51 of Roger Dedman's book 'Commonsense Punting':
"Using a theoretical race of 8 runners (the number is really immaterial as you will see later) with the favourite at $2 and your selection( for a place) at $6 to win.
Assume that evens and $6 are fair prices, so that F(fav) probability of winning is 1/2 (50%) and S (your selection ) probability is 1/6 ( 17%) . Between them they have 50% +17% = 67% = 2/3. So the probability of something else winning is 1/3 (33%).
From here on, the abbreviation PR (X) stands for the probability that the event X happens: e.g. PR (F) stands for the probability that the favourite wins.
If there are six other runners then each of them has a probability of winning of 1/16 ( one sixth of 1/3), assuming them all to have equal chances.
A place bet on S (your selection) will win in the event of any six of ( 6) distinct results:
(a) S wins: PR(S) = 1/6 = .1667
(b) F wins S 2nd PR (FS) = 1/2 x 1/3 = 1/6 = .1667
(c) an outsider wins, S 2nd PR(XS) = 1/3x 16/94 = .0588
(d) F wins S 3rd PR (FXS) = 1/2x2/3x16/44 = .1250
(e) F 2nd S 3rd PR (XFS) = 1/3 x 50/94 x 16/44 = .0662
(f) S 3rd , F unplaced: PR (XXS) = 1/3x 27/94x 16/89 = .0220
TOTAL .6054 These probabilities total .6054 or odds a little shorter than 4/6 so a place dividend equal to or better than $1.65 is acceptable."
This bit:
"If there are six other runners then each of them has a probability of winning of 1/16 ( one sixth of 1/3), assuming them all to have equal chances."
That assumption oversimplifies the calculation?
Without looking it up, the probability would be:
i) The probability of your horse winning
PLUS
ii) The probability of your horse winning a race where the winner is excluded
PLUS
iii) The probability of your horse winning a race where the winner and second placed horses are excluded.
The complication arises in figuring ii) and iii).
If you don't know who won the race you cannot calculate ii).
If you don't know who won and who came second you cannot calculate iii).
So you have to account for all outcomes.
Using an example of a 5 horse race where your horse is #3 and the market is 100% (nearly)
No 
Odds 
Probability 
1 
$2.00 
50.00% 
2 
$4.00 
25.00% 
3 
$6.00 
16.67% 
4 
$13.00 
7.69% 
5 
$100.00 
1.00% 
i) is trivially obvious. In your example ($6) the figure is 16.67%
ii) becomes a little more difficult to calculate.
If there are 5 horses and your horse is #3, then there are 4 outcomes that result in "success":
#1 wins and #3 comes second
#2 wins and #3 comes second
#4 wins and #3 comes second
#5 wins and #3 comes second
So you need to perform 4 calculations. Obviously as the number of runners increases the more calculations you have to make.
This is one formula for calculating coming second I came across  not intended for use but to display the complexity
(https://i.postimg.cc/yD1YZ3fC/probability2nd.png) (https://postimg.cc/yD1YZ3fC)
https://www.sportsbookreview.com/forum/handicapperthinktank/526381winvplaceoddsvaluemathquestion.html#post5076725
As for calculating iii) you will need a computer and a programming language that is a level above a spreadsheet IMO.
OR
You could divide the odds by 3 and account for the imperfections by maybe adding a premium to your required odds.
Me. I'd do the latter :lol:

The Dedman attempt is dead wrong. A recipe for ruin.
PP7's effort is another waste of time.
To calculate reasonable Place estimates for any runner, for a minimum you must consider the Odds or performances of every runner.
I believe I provided the formulas when responding to Bascoe's debut post.
Trying to simplify things will give you wildly incorrect answers.

I am not a mathematician and I don't bet each way and rarely bet for a place but I would think the "formula" would be similar to finding the length of a piece of string
You would need to treat each horse and each race on it's own merits, i.e. the opposition, the market place, track conditions on the day, trainer, Jockey etc I doubt there would be a "one size fits all" formula
Wenona was pretty much accurate with how I would look at it, if you were trying to find a placegetter behind Winx the win price would have zero relevance to the accurate Place dividend, a horse could be 20/1 or more to beat Winx but a $1.20 or shorter to run the drum, a race without Winx and it may be 4/1 the field, a 20/1 shot would be $6 or thereabouts the place, no doubt exaggerated examples to make the point........but Good luck with trying to find a formula to win at Punting...........
I find the formula to winning is you must be disciplined, you must have rules to follow but over all you must have knowledge and work bloody hard........you must have a staking plan and you always need some luck on your side......not luck long term, that comes with hard work....but luck on any given day.......and when Luck deserts you on a given day you must stay strong with what you know works, don't get off track and start thinking of ways to "win it all back" in one bet......find what works for YOU
Now that wasn't much help at all, was it??

JFC to follow on from your formula:
Foreach perm a,b,c
p=TrifectaProb(a,b,c)
Place[ a]+=p;
Place[ b]+=p;
Place[ c]+=p;
I am trying to get my head around what you have outlined.
For my own understanding, can I ask if the place probability is the sum of all instances of a runner (say 'a') in the calculation of the trifecta probability?
So the place probability for 'a' is it's probability in:
abc
acb
bac
bca
cab
cba
bascoe

In a 10 runner fields there are 720 perms.
72 of those have a first.
72 have a 2nd.
72 have a 3rd.
So you need to add up the probabilities of all 216 of those to get a's place probability.
You might have been asking that, but 216 much > 6.

I wasn’t terribly happy with the $8 a place on offer for a donkey with poor form in the 6th at Wagga today. Especially as it was $51 the win
So naturally I waited for Raceday and said donkey is now into $5.50 the win and $1.95 the place :lol: :lol: :lol:
Bouddi is its name for what it’s worth

Thanks jfc  that was what I thought you meant
For anyone else taking that approach I find running two harmonic means over all the perms before extracting the place percentages works well
The first sets the total % at 1 and provides a conservative estimate while running it using the bf back percentage/100 delivers a more aggressive place price
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