Statistics

This ActiverRecord plugin allows you to easily define and pull statistics for AR models. This plugin was built with reporting in mind.

Installation

script/plugin install git://github.com/acatighera/statistics.git

Examples

Defining statistics is similar to defining named scopes. Strings and symbols both work as names.

class Account < ActiveRecord::Base
  define_statistic :user_count, :count => :all
  define_statistic :average_age, :average => :all, :column_name => 'age'
  define_statistic 'subscriber count', :count => :all, :conditions => "subscription_opt_in = 1"
end

class Donations < ActiveRecord::Base
  define_statistic :total_donations, :sum => :all, :column_name => "amount"
end

Actually pulling the numbers is simple:

for all stats

Account.statistics                   # returns { :user_count => 120, :average_age => 28, 'subscriber count' => 74 }

for a single stat

Account.get_stat(:user_count)      # returns 120

Here are some additional benefits of using this plugin:

Easily Filter

Note: I found filtering to be an important part of reporting (ie. filtering by date). All filters are optional so even if you define them you don’t have to use them when pulling data. Using the filter_all_stats_on method and :joins options you can make things filterable by the same things which I found to be extremely useful.

class Account < ActiveRecord::Base
  define_statistic :user_count, :count => :all, :filter_on => { :state => 'state = ?', :created_after => 'DATE(created_at) > ?'}
  define_statistic :subscriber_count, :count => :all, :conditions => "subscription_opt_in = true"

  filter_all_stats_on(:account_type, "account_type = ?")
end

Account.statistics(:account_type => 'non-admin')
Account.get_stat(:user_count,  :account_type => 'non-admin',  :created_after => ‘2009-01-01’, :state => 'NY')

# NOTE: filters are optional (ie. no filters will be applied if none are passed in)
Account.get_stat(:user_count)

Standardized

All ActiveRecord classes now respond to statistics and get_stat methods

all_stats = []
[ Account, Post, Comment ].each do |ar|
  all_stats << ar.statistics
end

Calculated statistics (DRY)

You can define calculated metrics in order to perform mathematical calculations on one or more defined statistics.

class Account < ActiveRecord::Base
  has_many :donations

  define_statistic :user_count, :count => :all
  define_statistic :total_donations, :sum => :all, :column_name => 'donations.amount', :joins => :donations

  define_calculated_statistic :average_donation_per_user do
    defined_stats(:total_donations) / defined_stats(:user_count)
  end

  filter_all_stats_on(:account_type, "account_type = ?")
  filter_all_stats_on(:state, "state = ?")
  filter_all_stats_on(:created_after, "DATE(created_at) > ?")
end

Pulling stats for calculated metrics is the same as for regular statistics. They also work with filters like regular statistics!

Account.get_stat(:average_donation_per_user, :account_type => 'non-admin', :state => 'NY')
Account.get_stat(:average_donation_per_user, :created_after => '2009-01-01')

Reuse scopes you already have defined

You can reuse the code you have written to do reporting.

class Account < ActiveRecord::Base
  has_many :posts

  named_scope :not_admins, :conditions => “account_type = ‘non-admin’”
  named_scope :accounts_with_posts, :joins => :posts

  define_statistic :active_users_count, :count => [:not_admins, :accounts_with_posts]
end

Accepts all ActiveRecord::Calculations options

The :conditions and :joins options are all particularly useful

class Account < ActiveRecord::Base
  has_many :posts

  define_statistic :active_users_count, :count => :all, :joins => :posts, :conditions => "account_type = 'non-admin'"
end

Copyright (c) 2009 Alexandru Catighera, released under MIT license