Class: MathProbability::Probability

Inherits:
Object
  • Object
show all
Defined in:
lib/math_probability.rb

Overview

This class encapsulates mathimatical probability methods.

Class Method Summary collapse

Class Method Details

.combinations(objects, at_a_time) ⇒ Object 



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# File 'lib/math_probability.rb', line 26

def self.combinations(objects, at_a_time)
  (((objects.factoral)/((objects-at_a_time).factoral))*(1.0/(at_a_time.factoral))).to_i
end

.permutations_no_repeat(objects, at_a_time) ⇒ Object 



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# File 'lib/math_probability.rb', line 18

def self.permutations_no_repeat(objects, at_a_time)
  (objects.factoral)/(objects - at_a_time).factoral
end

.permutations_with_repeat(objects, at_a_time) ⇒ Object 



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# File 'lib/math_probability.rb', line 22

def self.permutations_with_repeat(objects, at_a_time)
  objects**at_a_time
end

.probability(choices, outcomes, reduce = true) ⇒ Object 



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# File 'lib/math_probability.rb', line 30

def self.probability(choices, outcomes, reduce=true)
  a = choices.to_f / outcomes
  answer = {decimal: a, percentage: "#{a*100}%", fraction: (reduce ? reduced_fraction(choices, outcomes) : "#{choices}/#{outcomes}")}
end

.sigma(start_seq, end_seq, seq_step) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/math_probability.rb', line 8

def self.sigma(start_seq, end_seq, seq_step)
  summnation ||= 0
  seq_step.gsub!(/((?![x-z0-9\s\.\-\+\*\/\(\)]).)*/,'').upcase!
  raise ArgumentError , "Only use x,y,z as variables" if (seq_step =~ /[A-Z]/).nil?
  (start_seq..end_seq).each do |value|
    summnation += eval(seq_step.gsub(/[X-Z]/,value.to_s))
  end
  summnation
end