Oddsmaker

Oddsmaker is to represent and manipulate betting odds. Multiple odds can be represented together, as a Market. A Market is able to calculate total probability and vig, and can also calculate true probabilities (total of 100%) and calculate overrounded odds (greater than 100%).

Oddsmaker can handle American odds, decimal odds, fractional odds, and implied probability, and allows for easy conversion between all of those types.

SportsBookReview has an excellent page which explains the different types of odds and converts between them.

This gem can be demoed at oddsmaker.herokuapp.com.

Installation

Add this line to your application's Gemfile:

gem 'oddsmaker'

And then execute:

$ bundle

Or install it yourself as:

$ gem install oddsmaker

Usage

Let's start with a simple odd:

# create an Odd
odd = Oddsmaker::Odd.american(300)  # => <Oddsmaker::Odd::American @id=300, @value=300>
odd = Oddsmaker::Odd.american('+300', 'underdog')  # optional 2nd param allows for identifying the odd
odd       # => <Oddsmaker::Odd::American @id="underdog", @value=300>
odd.name  # => "underdog"
odd.value # => 300
odd.to_s  # => "+300"

# can convert between formats
odd.decimal               # => <Oddsmaker::Odd::Decimal @id="underdog, @value=4.0>
odd.fractional            # => <Oddsmaker::Odd::Fractional @id="underdog, @value=(3/1)>
odd.implied_probability   # => <Oddsmaker::Odd::ImpliedProbability @id="underdog", @value=0.25>

# easy creation any type of odd
# any odd type can be compared as well
Oddsmaker::Odd.american(300) == Oddsmaker::Odd.decimal(4)
Oddsmaker::Odd.decimal(4) == Oddsmaker::Odd.fractional(3/1)
Oddsmaker::Odd.fractional(3/1) == Oddsmaker::Odd.implied(25)
Oddsmaker::Odd.implied(25) == Oddsmaker::Odd.american(300)

Oddsmaker::Odd.american(300, 'underdog').to_json # => {"name":"underdog","american":300,"decimal":4.0,"fractional":"3/1","implied":0.25}

A collection of Odds can be represented as a Market:

# Create a Market with odds as the arguments
market = Oddsmaker::Market.new(Oddsmaker::Odd.american(300), Oddsmaker::Odd.american(-400))
market.total_probability    # => 1.05
market.vig                  # => 0.04761904761904767 (equivalent to (1 - total_probability**-1))

# get the odds without vig
no_vig = market.without_vig   # => new market with the vig/overround removed
no_vig.odds                   # => [#<Oddsmaker::Odd::American @id=300, @value=320>, #<Oddsmaker::Odd::American @id=-400, @value=-320>]
no_vig.total_probability      # => 1.0
no_vig.vig                    # => 0

# apply an overround to have vigged odds
vigged = no_vig.overround!(5) # => 5% overround, returns a new Market
vigged.odds                   # => [#<Oddsmaker::Odd::American @id=300, @value=300>, #<Oddsmaker::Odd::American @id=-400, @value=-400>]
vigged.total_probability      # => 1.05
vigged.vig                    # => 0.04761904761904767

vigged == market              # => true # equality comparison only cares about the odds' values. Name and ordering is not relevant

There is also functionality for calculating wagers:

odd = Oddsmaker::Odd.american(300)  # => <Oddsmaker::Odd::American @id=300, @value=300>
wager = odd.wager(100)              # => <Oddsmaker::Wager @amount=100, @odd=#<Oddsmaker::Odd::American @id=300, @value=300>>
wager.amount                        # => 100
wager.profit                        # => 300
wager.return                        # => 400

# odds are able to calculate their own profit for a wager amount
odd.profit(100)                     # => 300

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/phoffer/oddsmaker.

License

The gem is available as open source under the terms of the MIT License.