Keith’s Blog

# Mostly inspired by 
# http://left.subtree.org/2007/01/15/creating-sparklines-with-jfreechart/
# have JFreeChart in your classpath, obviously, as well as jcommon.jar
require 'java'

module Graph
  class StackedBar
    include_class 'java.io.File'
    include_class 'org.jfree.chart.ChartUtilities'
    include_class 'org.jfree.chart.JFreeChart'
    include_class 'org.jfree.data.category.DefaultCategoryDataset'
    include_class 'org.jfree.chart.ChartFactory'
    include_class 'org.jfree.chart.plot.PlotOrientation'

    def initialize(width=600, height=400, data=[])
      @width = width
      @height = height
      dataset = create_sample_data() if data.empty?
      @chart = create_chart(dataset)
    end

    def render_to_file(filename, format="png")
      puts "Rendering graph to #{filename}"
      javafile = java.io.File.new(filename)
      ChartUtilities.saveChartAsPNG(javafile, @chart, @width, @height)
    end

    private
    def create_sample_data
      dataset = DefaultCategoryDataset.new
      dataset.addValue(1, "Submitted", "A")
      dataset.addValue(1, "Assigned", "A")
      dataset.addValue(3, "In-work", "A")
      dataset.addValue(1, "InVerfication", "A")
      dataset.addValue(2, "Delivered", "A")
      dataset.addValue(2, "Submitted", "B")
      dataset.addValue(1, "Rejected", "B")
      dataset.addValue(1, "Closed", "B")
      dataset.addValue(1, "Submitted", "C")
      dataset.addValue(1, "Assigned", "C")
      dataset.addValue(3, "In-work", "C")
      dataset.addValue(2, "On-hold", "C")

      return dataset
    end

    def create_chart(dataset)
      chart = ChartFactory.createStackedBarChart("XYZ's Development Projects",
                                                 "Project Name", 
                                                 "Hours", 
                                                 dataset,
                                                 PlotOrientation::VERTICAL, 
                                                 true, 
                                                 true, 
                                                 false)
      return chart    
    end
  end # class StackedBar  
end # class Graph

sb = Graph::StackedBar.new
sb.render_to_file("stacked_bar.png")

One Response to “Stacked Bar Charts in JRuby using JFreeChart”

1. enebo says:

   August 21, 2007 at 10:33 am

   I updated your blog entry code snippet to use the new more endorsed
   Java integration methods:
   1. Include Java
   2. Import instead of include_class

   In addition, I decided to play with the addValue method and see what I
   could come up with besides raw arrays (which is actually probably the
   best way of loading raw datasets) if you were handcoding a graph.

   I would be fun if we could get some threads going on list to discuss
   good rubification of Java API techniques…

   -Tom

   —– jfree.rb —-
   include Java

   import org.jfree.data.category.DefaultCategoryDataset

   class DefaultCategoryDataset
   class Inner
   def initialize(dataset, row)
   @dataset, @row = dataset, row.to_s
   end

   # a value of nil can call ‘removeValue’
   def []=(column, value)
   @dataset.addValue value, @row, column.to_s
   end

   def populate(hash)
   hash.each_with_pair do |column, value|
   @dataset.addValue value, @row, column.to_s
   end
   end
   end

   def [](row)
   Inner.new self, row
   end
   end

   module Graph
   class StackedBar
   import org.jfree.chart.ChartUtilities
   import org.jfree.chart.JFreeChart
   import org.jfree.chart.ChartFactory
   import org.jfree.chart.plot.PlotOrientation

   def initialize(width=600, height=400, dataset=create_sample_data)
   @height, @width, @chart = height, width, create_chart(dataset)
   end

   def render_to_file(filename, format=”png”)
   puts “Rendering graph to #{filename}”
   javafile = java.io.File.new(filename)
   ChartUtilities.saveChartAsPNG(javafile, @chart, @width, @height)
   end

   private
   def create_sample_data
   # I thought about method_missing for dataset.submitted but since these
   # can be arbitrary strings with method-name unfriendly chars in it I
   # decided against it.

   # This also allows symbols as well as strings
   dataset = DefaultCategoryDataset.new
   dataset[:Submitted].populate(:A => 1, :B => 2, :C => 3)
   dataset[:Assigned].populate(:A => 1, :C => 1)
   dataset["In-work"].populate(:A => 3, :C => 3)
   dataset[:InVerfication][:A] = 1
   dataset[:Delivered][:A] = 2
   dataset[:Rejected][:B] = 1
   dataset[:Closed][:B] = 1
   dataset["On-hold"][:C] = 2
   dataset
   end

   def create_chart(dataset)
   ChartFactory.createStackedBarChart(“XYZ’s Development Projects”,
   “Project Name”,
   “Hours”,
   dataset,
   PlotOrientation::VERTICAL,
   true,
   true,
   false)
   end
   end # class StackedBar
   end # class Graph

   sb = Graph::StackedBar.new
   sb.render_to_file(“stacked_bar.png”)