taiansu/Gemfile

## application.html.erb
<!DOCTYPE html>
<html>
  <head>
    <%# ... %>
    <%= include_gon %>
    <%= yield :head %>
  </head>
  <%# ... %>
</html>

## application.js.coffee
//= require raphael
//= require morris

window.chart_init = ->
  Morris.Line({
    element:  'records_chart'
    data:     $('#records_chart').data('records')
    xkey:     'date'
    ykeys:    ['total_amount'].concat(gon.chart_categories)
    labels:   ['Total_amount'].concat(gon.chart_categories)
    preUnits:  '$'
  })

## categories_controller.rb
class CategoriesController < ApplicationController
  # ...
  def show
    #...
    gon.chart_categories = @category.title

    respond_to do |format|
      format.html # show.html.erb
      format.json { render json: @category }
    end
  end
  # ...
end

## category...show.html.erb
<% content_for :head do %>
  <script type="text/javascript">
    $(function() {
        chart_init();
    });
  </script>
<% end %>
<%# ... %>

## Gemfile
gem 'raphael-rails'
gem 'morrisjs-rails'
gem 'gon'

#...

## record.rb
class Record < ActiveRecord::Base
# ......
  def self.total_grouped_by_day(start)
    records = where(date: start.beginning_of_day..Time.zone.today)
    records = records.group('date(date)')
    records = records.select('date, sum(amount) as total_amount')
    records = records.group_by{ |r| r.date.to_date}
  end

  def self.sum_of_category_by_day(start)
    records = where(date: start.beginning_of_day..Time.zone.today)
    records = records.group('category_id, date(date)')
    records = records.select('category_id, date, sum(amount) as total_amount')
    records = records.group_by{ |r| r.category_id }
    records.map do |category_id, value|
      value.group_by {|r| r.date.to_date}
    end
  end
end

## records...index.html.erb
<% content_for :head do %>
  <script type="text/javascript">
    $(function() {
        chart_init();
    });
  </script>
<% end %>
<%# ... %>

<%= content_tag :div, "", id: "records_chart", data:{records: records_chart_data} %>

## records_controller.rb
class RecordsController < ApplicationController
  # GET /records
  # GET /records.json
  def index
   gon.chart_categories = Category.all.map(&:title)

   # ...
  end

  # ...
end

## records_helper.rb
momodule RecordsHelper
  def records_chart_data(category = nil, start = 3.weeks.ago)
    total_by_day = Record.total_grouped_by_day(start)
    category_sum_by_day = Record.sum_of_category_by_day(start)

    (start.to_date..Time.zone.today).map do |date|
      chart_hash = {
        :date  => date,
        :total_amount => total_by_day[date].try(:first).try(:total_amount) || 0
      }
      Category.all.each_with_index do |category, index|
        chart_hash[category.title] = category_sum_by_day[index][date].try(:first).try(:total_amount) || 0
      end
      chart_hash
    end
  end
end
	<!DOCTYPE html>
	<html>
	<head>
	<%# ... %>
	<%= include_gon %>
	<%= yield :head %>
	</head>
	<%# ... %>
	</html>
	//= require raphael
	//= require morris

	window.chart_init = ->
	Morris.Line({
	element: 'records_chart'
	data: $('#records_chart').data('records')
	xkey: 'date'
	ykeys: ['total_amount'].concat(gon.chart_categories)
	labels: ['Total_amount'].concat(gon.chart_categories)
	preUnits: '$'
	})
	class CategoriesController < ApplicationController
	# ...
	def show
	#...
	gon.chart_categories = @category.title

	respond_to do \|format\|
	format.html # show.html.erb
	format.json { render json: @category }
	end
	end
	# ...
	end
	<% content_for :head do %>
	<script type="text/javascript">
	$(function() {
	chart_init();
	});
	</script>
	<% end %>
	<%# ... %>
	class Record < ActiveRecord::Base
	# ......
	def self.total_grouped_by_day(start)
	records = where(date: start.beginning_of_day..Time.zone.today)
	records = records.group('date(date)')
	records = records.select('date, sum(amount) as total_amount')
	records = records.group_by{ \|r\| r.date.to_date}
	end

	def self.sum_of_category_by_day(start)
	records = where(date: start.beginning_of_day..Time.zone.today)
	records = records.group('category_id, date(date)')
	records = records.select('category_id, date, sum(amount) as total_amount')
	records = records.group_by{ \|r\| r.category_id }
	records.map do \|category_id, value\|
	value.group_by {\|r\| r.date.to_date}
	end
	end
	end
	class RecordsController < ApplicationController
	# GET /records
	# GET /records.json
	def index
	gon.chart_categories = Category.all.map(&:title)

	# ...
	end

	# ...
	end
	momodule RecordsHelper
	def records_chart_data(category = nil, start = 3.weeks.ago)
	total_by_day = Record.total_grouped_by_day(start)
	category_sum_by_day = Record.sum_of_category_by_day(start)

	(start.to_date..Time.zone.today).map do \|date\|
	chart_hash = {
	:date => date,
	:total_amount => total_by_day[date].try(:first).try(:total_amount) \|\| 0
	}
	Category.all.each_with_index do \|category, index\|
	chart_hash[category.title] = category_sum_by_day[index][date].try(:first).try(:total_amount) \|\| 0
	end
	chart_hash
	end
	end
	end