Fortune

This gem allows you calculate the various statistical parameters and values.

Main features of the library are:

P - Probabilities
Odds - Calculation of odds
A, Pn, C - Combinatorics (accommodation, permutation, combinations)
Event - Random selection of events from the list

Requirements

ruby 1.9 or higher

Installation

Add this line to your application's Gemfile:

gem 'fortune'

And then execute:

$ bundle

Or install it yourself as:

$ gem install fortune

Usage

For Hash

Recalculation of the key values to probability, assuming that P = 1

{:a => 1, :b => 2, :c => 3}.to_p 
# => {:a=>0.16666666666666666, :b=>0.3333333333333333, :c=>0.5}

Select random key by value weights

{:a => 1, :b => 2, :c => 3}.choose 
# => return :c with 50% probability, :a ~ 16%, :b ~ 33%

Choose from set by value weights

{[:a, :b, :c] => 1, [:d] => 3}.choose_set 
# => return :d with 75% probability

Probability

Some methods for P

p = Fortune::P.new(:m => 1, :n => 10)
p = Fortune::P.new(1, 10)
p = Fortune::P.new(0.1)
# => #<Fortune::P:0x00000002316df0 @p=0.1>

p + p # => #<Fortune::P:0x0000000225e890 @p=0.2>
p * p # => #<Fortune::P:0x000000022602a8 @p=0.010000000000000002>

p.to_percent # => 10.0

p.odds # => #<Fortune::Odds:0x0000000230ff50 @p=0.1, @s=1, @k=9.0, @type=:on_win>
p.odds.to_s # => "1:9.0 on_win (p: 10.00%)"

Check event is occured

Fortune::P.is(1,10) # => false (90%)

Select random element

Fortune::P.n(3) # => 1 or 2 or 3

Select random key from array or range by weights ({P.n(key) => weight, ...}, P(sum(weights)) = 1)

Fortune::P.n_select(10 => 1, 5 => 1000) # => 4
Fortune::P.n_select((1..10) => 1, (100..200) => 1000) # => 157
Fortune::P.n_select([:a,:b,:c] => 1, [:d,:e] => 1000) # => :d

Odds

Class for odds calculations

odds = Fortune::Odds.new(:win => 5, :lose => 6)
# => #<Fortune::Odds:0x000000026ccf08 @p=0.45454545454545453, @s=5, @k=6, @type=:on_win>
odds_other = Fortune::Odds.new(:s => 5, :k => 7)
# => #<Fortune::Odds:0x00000002706168 @p=0.4166666666666667, @s=5, @k=7, @type=:on_win>
odds > odds_other # => true
odds.variants # => 11
odds.p # => 0.45454545454545453

Large values can be simple converted to human view

Fortune::Odds.new(:win => 1345, :lose => 3623).to_s # => "1345:3623 on_win (p: 27.07%)"
Fortune::Odds.new(:win => 1345, :lose => 3623).to_human.to_s # => "2:5 on_win (p: 28.57%)"
Fortune::Odds.new(:win => 1345, :lose => 3623).to_human(:k => 5, :fractions => true).to_s # => "1.5:4 on_win (p: 27.27%)"

Reverse odds to lose

odds = Fortune::Odds.new(:win => 5, :lose => 6)
# => #<Fortune::Odds:0x00000002822e98 @p=0.45454545454545453, @s=5, @k=6, @type=:on_win>
odds.revert
# => #<Fortune::Odds:0x00000002822e98 @p=0.5454545454545454, @s=6, @k=5, @type=:on_win>
odds.to_lose
# => #<Fortune::Odds:0x00000002822e98 @p=0.5454545454545454, @s=5, @k=6, @type=:on_lose>

Combinatorics

Accomodation (A)

Permutation without repetition with select k elements.

Example: 20 different elements and you need select 5 of them (how many ways of selection exists?). Elements is ordered ([a,b,c] != [b,c,a])

Fortune::A.calc(:elements => 10, :select => 5) # => 30240

Permutation

Permutation without repetition (Pn)

Example: the amount of distributions of the four teams in four places

Fortune::Pn.calc(4) # => 24

other examples

Fortune::Pn.calc(:elements => 5) # => 120
Fortune::Pn.calc(:elements => 5, :select => 2) # => 20

Permutation with repetition (Pnr)

Example: how many different options you can dress up if there are three sweaters two skirts and two hats (322, if all thing is equal 3, then: Pn_repetition(:n => 3, :k => 3), k - element groups, n - elements count in group)

Fortune::Pn_repetition(:n => 3, :k => 3) # => 27
is equal to
Fortune::Pnr(:groups => 3, :elements => 3) # => 27 (human like variant)

Combinations

Combinations without repetition (C)

Example: 10 different elements (students) and you need select 5 of them (how many ways of selection exists?). Elements does not ordered ([a,b,c] == [b,c,a])

Fortune::C.calc(:elements => 10, :select => 5) # => 252

Combination with repetition (Cr)

Fortune::C_repetition.calc(:elements => 10, :select => 5) # => 2002
same as
Fortune::Cr.calc(:elements => 10, :select => 5) # => 2002

Addon Class Methods

Math.factorial(n)

Event class - under development

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request

Authors

Personal blog author: Malykh Oleg - blog in russian

fortune

Development