01_daily_stats_report.rb

class DailyStatsReport < KPI::Report
  def users
    result 'Users', User.count, :description => 'Total users count'
  end

  def premium_users
    result 'Premium users', User.premium.count
  end

  def premium_users_percentage
    result 'Premium users', premium_users.to_f / users * 100, :unit => '%'
  end

  def income
    result 'Total income', Order.paid.sum(:total), :unit => 'EUR'
  end

  def daily_income
    result 'Daily income', Order.paid.where(:created_at => the_day).sum(:total), :unit => 'EUR'
  end

  private

  def the_day
    @yesterday ||= begin
      yesterday = (time - 1.day)
      yesterday.beginning_of_day..yesterday.end_of_day
    end
  end
end

02_instantiating_report.rb

report = DailyStatsReport.new

03_getting_value.rb

> report.users
=> #<KPI::Entry:0x10177f630 @name="Users", @unit=nil, @description="Total users count", @value=874>

04_enumerator.rb

> report.entries.map(&:value)
=> [874, 14, 138.6, 19.8]

05_historical_report.rb

report = DailyStatsReport.new(:time => 1.day.ago)

06_diff_report.rb

report_today = DailyStatsReport.new
report_yesterday = DailyStatsReport.new(:time => 1.day.ago)
diff_report = KPI::MergedReport.new(report_today, report_yesterday) do |entry_today, entry_yesterday|
  KPI::Entry.new '$$ (change)', entry_today.value - entry_yesterday.value
end

07_using_diff_report.rb

> diff_report.premium_users
=> #<KPI::Entry:0x11577e319 @name="Premium users (change)", @unit=nil, @description="", @value=2>

08_average_report.rb

avg_report = KPI::MergedReport.new(*week_reports) do |*entries|
  KPI::Entry.new '$$ (avg)', entries.map(&:value).inject(:+).to_f / entries.size
end