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Enumerable::Statistics provides some methods to calculate statistical summary in arrays and enumerables.


Add this line to your application's Gemfile:

gem 'enumerable-statistics'

And then execute:

$ bundle

Or install it yourself as:

$ gem install enumerable-statistics


You should load this library by the following line in your script at first.

require 'enumerable/statistics'

The following methods are supplied by this library:

  • Array#mean, Enumerable#mean
    • Calculates a mean of values in an array or an enumerable
  • Array#variance, Enumerable#variance
    • Calculates a variance of values in an array or an enumerable
  • Array#stdev, Enumerable#stdev
    • Calculates a standard deviation of values in an array or an enumerable
  • Array#mean_variance, Enumerable#mean_variance
    • Calculates a mean and a variance simultaneously
  • Array#mean_stdev, Enumerable#mean_stdev
    • Calculates a mean and a standard deviation simultaneously

Moreover, for Ruby < 2.4, Array#sum and Enumerable#sum are provided.

All methods scan a collection once to calculate statistics and preserve precision as possible.


$ bundle exec rake bench
# sum
Warming up --------------------------------------
              inject     1.545k i/100ms
               while     2.342k i/100ms
                 sum    11.009k i/100ms
Calculating -------------------------------------
              inject     15.016k (± 9.6%) i/s -     75.705k in   5.098723s
               while     22.238k (±16.2%) i/s -    107.732k in   5.068156s
                 sum    112.992k (± 6.9%) i/s -    572.468k in   5.091868s
# mean
Warming up --------------------------------------
              inject     1.578k i/100ms
               while     2.057k i/100ms
                mean     9.855k i/100ms
Calculating -------------------------------------
              inject     15.347k (± 8.6%) i/s -     77.322k in   5.076009s
               while     21.669k (±14.5%) i/s -    106.964k in   5.074312s
                mean    108.861k (± 8.9%) i/s -    542.025k in   5.021786s
# variance
Warming up --------------------------------------
              inject   586.000  i/100ms
               while   826.000  i/100ms
            variance     8.475k i/100ms
Calculating -------------------------------------
              inject      6.187k (± 6.7%) i/s -     31.058k in   5.043418s
               while      8.597k (± 7.4%) i/s -     42.952k in   5.024587s
            variance     84.702k (± 8.5%) i/s -    423.750k in   5.039936s


After checking out the repo, run bin/setup to install dependencies. 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/mrkn/enumerable-statistics.