application_controller.rb

def open_flash_chart(height, width, data_url, div_name = nil)
    options = {}
    options[:height] = height
    options[:width] = width
    options[:swf_file_name] = "flash/open-flash-chart.swf"
    options[:div_name] = div_name unless div_name.nil?
    open_flash_chart_object_from_hash(data_url, options)
  end

stat.rb

def Stat.signups_per_day
    Rails.cache.fetch("Stat.signups_per_day", :expires_in => 1.day) do
      signups = {}
      %w{trial guest registered}.each do |role|
        recs = User.find_by_sql(["select date(users.created_on) as date, count(*) as signup_count from users where role = ? group by date order by date ASC", role])
        signups[role] = {}
        recs.map {|rec| signups[role][rec.date] = rec.signup_count}
      end
      signups
    end
  end

stat_controller.rb

  def signups_per_day
    #irrelevant code elided
    @flash_chart_trials = open_flash_chart(550, 530, "/stats/signups-per-day-chart/trial", "trial_signups_chart")
    @flash_chart_guests = open_flash_chart(550, 530, "/stats/signups-per-day-chart/guest", "guests_signups_chart")
  end

  #route is /stats/signups-per-day-chart/:role
  def signups_per_day_chart
    raise "That is not a valid role!" unless %w{trial guest}.include? params[:role]
    title = Title.new("BCC Signups (#{params[:role].titleize.pluralize})")

    signups = Stat.signups_per_day[params[:role]]
    first_day = Date.parse("2009-07-05")

    bar = BarGlass.new
    day_values = Rails.cache.fetch("StatController.signups_per_day:#{params[:role]}", :expires_in => 1.day) do
      (first_day..(Date.today)).map {|date| (signups[date.to_s] || 0).to_i }
    end

    maximum_signups = 0
    
    week_values = day_values.in_groups_of(7).map do |week|
      signups_in_this_week = week.reject {|a| a.nil?}.sum
      maximum_signups = signups_in_this_week if signups_in_this_week > maximum_signups
      tooltip_for_this_week = (["Total: #{signups_in_this_week}"] + week.map {|day| day || 0}).join("<br>")
      val = BarValue.new(signups_in_this_week)
      val.set_tooltip(tooltip_for_this_week)
      val
    end

    bar.values = week_values

    x_axis = XAxis.new
    x_axis.steps = 7
    labels = XAxisLabels.new
    day_labels = (first_day..(Date.today)).map {|date| date.to_s }
    week_labels = day_labels.in_groups_of(7).map {|week| "#{week.first} ~ #{week.last}"}
    labels.labels = week_labels
    labels.set_vertical
    x_axis.labels = labels

    y_axis = YAxis.new
    scaling_factor = 100
    maximum_signups = ((maximum_signups / scaling_factor) + 1) * scaling_factor
    y_axis.set_range(0, maximum_signups, scaling_factor)

    chart = OpenFlashChart.new
    chart.set_title(title)
    chart.y_axis = y_axis
    chart.x_axis = x_axis
    chart.add_element bar
    render :text => chart.to_s
  end