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How to Update the Ratings in the Event of Non-Runners

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One of the problems all backers face is the change to the shape of a race caused by non-runners which are declared late. This can reach epidemic proportions at the minor tracks, particularly if there is a sudden change in the going, or if the advance going report proves to be inaccurate.

Whenever possible, every effort is made to re-run the program over the remaining runners and create a set of updated ratings.  These are sent out around lunchtime on the day of the race in question.

However, there are occasions when trainers withdraw horses very late, and further updating of the ratings is just not practicable.  This is the situation where the update formula comes into play.  All that is required is a pocket calculator.

 As far as HOOF ratings are concerned, if the non-runner in question is given a very low rating, then the net effect is likely to be minimal. However, in some cases one or more late withdrawals can radically affect the ratings of other horses in the race.

 The important thing is to be able reliably to redistribute the probability rating(s) given to the withdrawn horse(s) among the other runners. This can be done quite simply with a pocket calculator in the following manner.
 

  1. Add up the probabilities of the remaining horses (the figures in the extreme left-hand column) after the deletion of any non-runner(s) or subtract the probabilities of the withdrawn horse(s) from 1 (whichever is easier). Let the resulting figure be the sum of remaining probabilities.

    2.  
  2. For each any horse whose rating you wish to recalculate divide that horse's true probability rating by the sum of remaining probabilities. We now have a proportionally adjusted true probability rating for the horse or horses in question.

    3.  
  3. To find the V-30 probability rating, deduct 30% from the proportionally adjusted true probability rating.

    4.  
  4. To find the V-30 odds find the odds corresponding to the new V-30 probability rating in the Probability to Odds conversion table given below.

    5.  
  5. To find the V-PLUS odds, calculate the new  proportionally adjusted true probability rating and use the Probability to Odds conversion table below to calculate the corresponding TR-ODDs. Then use the True Odds to V-Plus conversion table to work out the V-Plus odds.

    6.  

     
     
     
     
     

     Here is a simple worked example:

                          Southwell:12.45
                         Handicap chase:12 rnrs
    HORSE                TR-PROB TR-ODDS   V-30  V-PLUS
    Un Jour A Vassy(FR)    0.33   85-40    10-3    9-2
    Tonoco                 0.19     9-2    13-2    9-1 Non-runner
    Nordic Crest(IRE)      0.104    9-1    14-1   18-1

    In Question            0.087   11-1    16-1   22-1
    Connor Macleod(IRE)    0.068   14-1    20-1   28-1
    Native Wit(IRE)        0.063   16-1    22-1   33-1
    Monnaie Forte(IRE)     0.059   16-1    25-1   33-1
    Mazileo                0.037   28-1    40-1   66-1
    Prince Sorinieres(FR)  0.023   50-1    66-1  100-1
    Stately Home(IRE)      0.012  100-1   150-1  200-1
    Sir Dante(IRE)         0.012  100-1   150-1  200-1
    Father Rector(IRE)     0.008  150-1   200-1  300-1

       


    Let's assume we wish to recalculate the TR-PROB and V-30 odds for  top-rated Un Jour A Vassy.
     

    1. Subtract Tonoco's TR-PROB from 1.  (1 - 0.19 = 0.81)

      2.  
    2. Divide Un Jour A Vassy's TR-PROB by this figure (0.33/0.81 = 0.407.  This is his new TR-PROB)

      3.  
    3. To calculate the V-30 probability , simply deduct 30% from the new TR-PROB.  E.g. 0.47 - (0.47*30/100) = 0.329

      4.  
    4. Use the probability to odds conversion table below to convert the resulting probability into the corresponding odds = 85/40.
    Assuming that we want to recalculate the TR-PROB and V-PLUS odds for Un Jour A Vassy repeat steps 1-2. Then:

        3.    Using the probability to odds conversion table below, convert the new TR-PROB to the corresponding odds.
                0.47 = 6/5

        4.    Use the true odds to V-PLUS conversion table to convert the new odds into the corresponding V-PLUS odds. 6/5 -> 5/2
     


     

    Probability to Odds Conversion Table
    To read off the odds corresponding to the TR-PROB you wish to convert, simply locate the TR-PROB in the appropriate 'HI-LO' range.

    Thus a TR-PROB of 0.352 corresponds to odds of 15/8, and a TR-PROB of 0.139 corresponds to odds of 13/2.

    To belong within a particular range, the TR-ODDS must be greater than the figure in the HI column and at least equal to the figure in the LO column.  Thus 0.499 counts as 11-10, and 0.5 counts as even money.
     

    HI          LO        ODDS

    1.000      0.733      '4-11'
    0.733      0.714       '2-5'
    0.714      0.692       '4-9'
    0.692      0.666       '1-2'
    0.666      0.636       '4-7'
    0.636      0.619      '8-13'
    0.619      0.6         '4-6'
    0.6        0.578      '8-11'
    0.578      0.555       '4-5'
    0.555      0.545       '5-6'
    0.545      0.523     '10-11'
    0.523      0.5       'EVENS'
    0.5        0.476     '11-10'
    0.476      0.454       '6-5'
    0.454      0.444       '5-4'
    0.444      0.421      '11-8'
    0.421      0.4         '6-4'
    0.4        0.380      '13-8'
    0.380      0.363       '7-4'
    0.363      0.347      '15-8'
    0.347      0.333       '2-1'
    0.333      0.32,     '85-40'
    0.32       0.307       '9-4'
    0.307      0.285       '5-2'
    0.285      0.266      '11-4'
    0.266      0.25        '3-1'
    0.25       0.230      '10-3'
    0.230      0.222       '7-2'
    0.222      0.2,        '4-1'
    0.2        0.181       '9-2'
    0.181      0.166       '5-1'
    0.166      0.153      '11-2'
    0.153      0.142       '6-1'
    0.142      0.133      '13-2'
    0.133      0.117      '15-2'
    0.117      0.111       '8-1'
    0.111      0.1         '9-1'
    0.1        0.090      '10-1'
    0.090      0.083      '11-1'
    0.083      0.076      '12-1'
    0.076      0.066      '14-1'
    0.066      0.058      '16-1'
    0.058      0.052      '18-1'
    0.052      0.047      '20-1'
    0.047      0.043      '22-1'
    0.043      0.038      '25-1'
    0.038      0.034      '28-1'
    0.034      0.029      '33-1'
    0.029      0.024      '40-1'
    0.024      0.019      '50-1'
    0.019      0.014      '66-1'
    0.014      0.009     '100-1'
    0.009      0.006     '150-1'
    0.006      0.004     '200-1'
    0.004      0.003     '250-1'
    0.003      0.001     '500-1'
    0.001      0.000     'NOBET'
    0.000      0.000     'NOBET'
     


     

    True Odds to V-Plus Conversion Table
     

    TR-ODDS    V-PLUS
    1-3        1-1
    4-11      11-10
    2-5       11-10
    4-9         6-5
    1-2         5-4
    8-15       11-8
    4-7        11-8
    8-13        6-4
    4-6         6-4
    8-11       13-8
    4-5         7-4
    5-6         7-4
    10-11      15-8
    EVENS       2-1
    11-10       9-4
    6-5         5-2
    5-4         5-2
    11-8       11-4
    6-4         3-1
    13-8       10-3
    7-4         7-2
    15-8        4-1
    2-1         4-1
    85-40       9-2
    9-4         9-2
    5-2         5-1
    11-4       11-2
    3-1         6-1
    10-3        7-1
    7-2         7-1
    4-1         8-1
    9-2         9-1
    5-1        10-1
    11-2       11-1
    6-1        12-1
    13-2       14-1
    7-1        14-1
    15-2       16-1
    8-1        16-1
    17-2       18-1
    9-1        18-1
    10-1       20-1
    11-1       22-1
    12-1       25-1
    14-1       28-1
    16-1       33-1
    18-1       40-1
    20-1       40-1
    22-1       50-1
    25-1       50-1
    28-1       66-1
    33-1       66-1
    40-1       80-1
    50-1      100-1
    66-1      150-1
    100-1     200-1
    150-1     300-1
    200-1     400-1
    250-1     500-1
    500-1     NOBET
    NOBET     NOBET
     

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