Class: Rubythinking::Distributions::Binomial

Inherits:
Object
  • Object
show all
Defined in:
lib/rubythinking/distributions/binomial.rb

Class Method Summary collapse

Class Method Details

.density(value:, size:, success:) ⇒ Object 



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# File 'lib/rubythinking/distributions/binomial.rb', line 8

def density(value:, size:, success:)
  # Use variable names often used in math
  # textbooks and wikipedia to have code
  # close to the formula
  k = value
  n = size
  p = success

  (factorial(n).to_f / (factorial(k) * factorial(n - k))).to_f * (p**k) * ((1-p)**(n-k))
end

.factorial(n) ⇒ Object 



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# File 'lib/rubythinking/distributions/binomial.rb', line 19

def factorial(n)
  return 1 if n < 1
  n.to_i.downto(1).inject(:*)
end

.likelihood(w, l, p) ⇒ Object 



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# File 'lib/rubythinking/distributions/binomial.rb', line 25

def likelihood(w, l, p)
  density(value: w, size: (w+l), success: p)
end

.samples(n, size:, success:) ⇒ Object 



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# File 'lib/rubythinking/distributions/binomial.rb', line 3

def samples(n, size:, success:)
  dist = Croupier::Distributions::Binomial.new(size: size, success: success)
  samples = dist.to_enum.take(n)
end