Class: Skab::Models::Binomial

Inherits:
Object
  • Object
show all
Defined in:
lib/skab/models/binomial.rb

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(args) ⇒ Binomial

Returns a new instance of Binomial.



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# File 'lib/skab/models/binomial.rb', line 5

def initialize(args)
  @a_trials = args.shift.to_i
  @a_success = args.shift.to_i
  @b_trials = args.shift.to_i
  @b_success = args.shift.to_i
  @fact = { }
end

Class Method Details

.help ⇒ Object 



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# File 'lib/skab/models/binomial.rb', line 64

def self.help
  "skab [output] binomial [trials_a] [successes_a] [trials_b] [successes_b]\n\\tWhere: all parameters are integers\n\\tPlots the binomial distribution for A and B, given their respective\n\\tnumber of successes and trials\n  HELP\nend\n"

Instance Method Details

#differential ⇒ Object 



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# File 'lib/skab/models/binomial.rb', line 38

def differential
  return @differential if @differential
  @differential = Hash.new(0)
  i = 0.0
  while i <= 1000
    j = 0.0
    while j <= 1000
      @differential[(j - i) / 1000] += distribution[j][2] * distribution[i][1] / 1000
      j += 1
    end
    i += 1
  end
  @differential
end

#distribution ⇒ Object 



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# File 'lib/skab/models/binomial.rb', line 13

def distribution
  return @distribution if @distribution
  @distribution = []
  sums = [0, 0, 0]
  i = 0.0
  while i <= 1000
    @distribution[i] = []
    @distribution[i][0] = i / 1000
    @distribution[i][1] = binomial(@a_trials, @a_success, i / 1000)
    @distribution[i][2] = binomial(@b_trials, @b_success, i / 1000)
    sums[1] += binomial(@a_trials, @a_success, i / 1000)
    sums[2] += binomial(@b_trials, @b_success, i / 1000)
    i += 1
  end
  i = 0.0
  while i <= 1000
    @distribution[i][1] /= sums[1]
    @distribution[i][1] *= 1000
    @distribution[i][2] /= sums[2]
    @distribution[i][2] *= 1000
    i += 1
  end
  @distribution
end

#percentile(p) ⇒ Object 



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# File 'lib/skab/models/binomial.rb', line 53

def percentile(p)
  sum = 0.0
  Hash[differential.sort].each do |k, v|
    sum += v
    if sum >= p * 1000
      return k
    end
  end
  percentile
end