124 lines
4.1 KiB
Elixir
124 lines
4.1 KiB
Elixir
defmodule Glicko.Player do
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@moduledoc """
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A convenience wrapper that handles conversions between glicko versions one and two.
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## Usage
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Create a player with the default values for an unrated player.
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iex> Player.new_v2
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%Player{version: :v2, rating: 0.0, rating_deviation: 2.014761872416068, volatility: 0.06}
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Create a player with custom values.
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iex> Player.new_v2([rating: 1500, rating_deviation: 50, volatility: 0.05])
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%Player{version: :v2, rating: 1500, rating_deviation: 50, volatility: 0.05}
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Convert a *v2* player to a *v1*. Note this drops the volatility.
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iex> Player.new_v2 |> Player.to_v1
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%Player{version: :v1, rating: 1.5e3, rating_deviation: 350.0, volatility: nil}
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Convert a *v1* player to a *v2*.
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iex> Player.new_v1 |> Player.to_v2(0.06)
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%Player{version: :v2, rating: 0.0, rating_deviation: 2.014761872416068, volatility: 0.06}
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Note calling `to_v1` with a *v1* player or likewise with `to_v2` and a *v2* player
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will pass-through unchanged. The volatility arg in this case is ignored.
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iex> player_v2 = Player.new_v2
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iex> player_v2 == Player.to_v2(player_v2)
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true
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"""
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@magic_version_scale 173.7178
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@magic_version_scale_rating 1500.0
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@default_v1_rating 1500.0
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@default_v1_rating_deviation 350.0
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@default_v2_volatility 0.06
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@type t :: v1_t | v2_t
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@type v1_t :: %__MODULE__{version: :v1, rating: float, rating_deviation: float, volatility: nil}
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@type v2_t :: %__MODULE__{version: :v2, rating: float, rating_deviation: float, volatility: float}
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defstruct [
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:version,
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:rating,
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:rating_deviation,
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:volatility,
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]
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@doc """
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Creates a new v1 player.
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If not overriden, will use default values for an unrated player.
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"""
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@spec new_v1([rating: float, rating_deviation: float]) :: v1_t
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def new_v1(opts \\ []), do: %__MODULE__{
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version: :v1,
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rating: Keyword.get(opts, :rating, @default_v1_rating),
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rating_deviation: Keyword.get(opts, :rating_deviation, @default_v1_rating_deviation),
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volatility: nil,
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}
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@doc """
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Creates a new v2 player.
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If not overriden, will use default values for an unrated player.
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"""
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@spec new_v2([rating: float, rating_deviation: float, volatility: float]) :: v2_t
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def new_v2(opts \\ []), do: %__MODULE__{
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version: :v2,
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rating: Keyword.get(opts, :rating, @default_v1_rating |> scale_rating_to(:v2)),
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rating_deviation: Keyword.get(opts, :rating_deviation, @default_v1_rating_deviation |> scale_rating_deviation_to(:v2)),
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volatility: Keyword.get(opts, :volatility, @default_v2_volatility),
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}
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@doc """
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Converts a v2 player to a v1.
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A v1 player will pass-through unchanged.
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Note the volatility field used in a v2 player will be lost in the conversion.
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"""
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@spec to_v1(player :: t) :: v1_t
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def to_v1(player = %__MODULE__{version: :v1}), do: player
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def to_v1(player = %__MODULE__{version: :v2}), do: new_v1([
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rating: player.rating |> scale_rating_to(:v1),
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rating_deviation: player.rating_deviation |> scale_rating_deviation_to(:v1),
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])
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@doc """
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Converts a v1 player to a v2.
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A v2 player will pass-through unchanged with the volatility arg ignored.
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"""
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@spec to_v2(player :: t, volatility :: float) :: v2_t
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def to_v2(player, volatility \\ @default_v2_volatility)
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def to_v2(player = %__MODULE__{version: :v2}, _volatility), do: player
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def to_v2(player = %__MODULE__{version: :v1}, volatility), do: new_v2([
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rating: player.rating |> scale_rating_to(:v2),
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rating_deviation: player.rating_deviation |> scale_rating_deviation_to(:v2),
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volatility: volatility,
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])
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@doc """
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Scales a players rating.
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"""
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@spec scale_rating_to(rating :: float, to_version :: :v1 | :v2) :: float
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def scale_rating_to(rating, :v1), do: (rating * @magic_version_scale) + @magic_version_scale_rating
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def scale_rating_to(rating, :v2), do: (rating - @magic_version_scale_rating) / @magic_version_scale
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@doc """
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Scales a players rating deviation.
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"""
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@spec scale_rating_deviation_to(rating_deviation :: float, to_version :: :v1 | :v2) :: float
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def scale_rating_deviation_to(rating_deviation, :v1), do: rating_deviation * @magic_version_scale
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def scale_rating_deviation_to(rating_deviation, :v2), do: rating_deviation / @magic_version_scale
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end
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