CategoricalDistribution

This gem provides an implementation of a categorical distribution using Vose's Alias Method. More details on the implementation can be found here. The algorithm chooses a random item, with a weighted probability given on initialization, in constant time, after an O(n) initialization step.

Add this line to your application's Gemfile:

gem 'categorical_distribution'

And then execute:

$ bundle

Or install it yourself as:

$ gem install categorical_distribution

r = CategoricalDistribution.new({ a: 1, b: 2, c: 3 })
r.rand    #=> :a
r.rand    #=> :b
r.rand    #=> :c
r.rand    #=> :c
r.rand    #=> :b

r = CategoricalDistribution.new([1, 1, 1])
r.take(5) #=> [1, 2, 1, 1, 2]

r = CategoricalDistribution.new([1, 3], ['heads', 'tails'])
r.rand    #=> "tails"
r.rand    #=> "tails"
r.rand    #=> "tails"
r.rand    #=> "tails"
r.rand    #=> "heads"

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/zanecodes/categorical_distribution.

The gem is available as open source under the terms of the MIT License.