Class Gruff::Pie
In: lib/gruff/pie.rb
Parent: Gruff::Base

Here‘s how to make a Pie graph:

  g = Gruff::Pie.new
  g.title = "Visual Pie Graph Test"
  g.data 'Fries', 20
  g.data 'Hamburgers', 50
  g.write("test/output/pie_keynote.png")

To control where the pie chart starts creating slices, use zero_degree.

Methods

Constants

TEXT_OFFSET_PERCENTAGE = 0.15

Attributes

zero_degree  [RW]  Can be used to make the pie start cutting slices at the top (-90.0) or at another angle. Default is 0.0, which starts at 3 o‘clock.

Public Instance methods

[Source]

# File lib/gruff/pie.rb, line 27
  def draw
    @hide_line_markers = true
    
    super

    return unless @has_data

    diameter = @graph_height
    radius = ([@graph_width, @graph_height].min / 2.0) * 0.8
    top_x = @graph_left + (@graph_width - diameter) / 2.0
    center_x = @graph_left + (@graph_width / 2.0)
    center_y = @graph_top + (@graph_height / 2.0) - 10 # Move graph up a bit
    total_sum = sums_for_pie()
    prev_degrees = @zero_degree

    # Use full data since we can easily calculate percentages
    data = (@sort ? @data.sort{ |a, b| a[DATA_VALUES_INDEX].first <=> b[DATA_VALUES_INDEX].first } : @data)
    data.each do |data_row|
      if data_row[DATA_VALUES_INDEX].first > 0
        @d = @d.stroke data_row[DATA_COLOR_INDEX]
        @d = @d.fill 'transparent'
        @d.stroke_width(radius) # stroke width should be equal to radius. we'll draw centered on (radius / 2)

        current_degrees = (data_row[DATA_VALUES_INDEX].first / total_sum) * 360.0 

        # ellipse will draw the the stroke centered on the first two parameters offset by the second two.
        # therefore, in order to draw a circle of the proper diameter we must center the stroke at
        # half the radius for both x and y
        @d = @d.ellipse(center_x, center_y, 
                  radius / 2.0, radius / 2.0,
                  prev_degrees, prev_degrees + current_degrees + 0.5) # <= +0.5 'fudge factor' gets rid of the ugly gaps
                  
        half_angle = prev_degrees + ((prev_degrees + current_degrees) - prev_degrees) / 2
        
        # Following line is commented to allow display of the percentiles
        # bug appeared between r90 and r92
        # unless @hide_line_markers then
          # End the string with %% to escape the single %.
          # RMagick must use sprintf with the string and % has special significance.
          label_string = ((data_row[DATA_VALUES_INDEX].first / total_sum) *
                          100.0).round.to_s + '%%'
          @d = draw_label(center_x,center_y, half_angle,
                          radius + (radius * TEXT_OFFSET_PERCENTAGE),
                          label_string)
        # end

        prev_degrees += current_degrees
      end
    end

    # TODO debug a circle where the text is drawn...
    
    @d.draw(@base_image)
  end

[Source]

# File lib/gruff/pie.rb, line 22
  def initialize_ivars
    super
    @zero_degree = 0.0
  end

[Validate]