Class: Selection::RankSampling

Inherits:

Object

• Object
• Selection::RankSampling

show all

Defined in:

../lib/rank_sampling.rb

Overview

Instance Attribute Summary (collapse)

• - (Object) population

  The population to select from.

Instance Method Summary (collapse)

• - (RankSampling) initialize(ranker) constructor

  Set the instance of the Ranking object which will be used for ranking the population before the selection.

• - (Object) random=(rnd)

  Set the source of randomness for the roulette, using Sampling#random=.

• - (Object) select(how_much, population = self.population)

  Rank the population and then select individuals from it.

• - (Object) select_one(population = self.population)

  Rank the population and then select one individual from it.

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# File '../lib/rank_sampling.rb', line 16

def initialize ranker
  raise "RankSampling: invalid Ranking object" unless ranker.kind_of? Ranking     
  @ranker = ranker
  @sampling = Sampling.new :proportion
  @population = nil     
end

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# File '../lib/rank_sampling.rb', line 24

def population
  @population
end

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# File '../lib/rank_sampling.rb', line 27

def random= rnd
  @sampling.random = rnd
end

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# File '../lib/rank_sampling.rb', line 33

def select( how_much, population=self.population )
  ranked = @ranker.rank( population ) 
  @population = population
 
  @sampling.select( how_much, ranked ).map { |individual| individual.original }
end

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# File '../lib/rank_sampling.rb', line 42

def select_one population=self.population
  select( 1, population ).first
end