Class: Gruff::Pie

Inherits:
Base
  • Object
show all
Defined in:
lib/gruff/pie.rb

Overview

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.

Direct Known Subclasses

Mini::Pie

Constant Summary collapse

TEXT_OFFSET_PERCENTAGE = 
0.15

Constants inherited from Base

Base::DATA_COLOR_INDEX, Base::DATA_LABEL_INDEX, Base::DATA_VALUES_INDEX, Base::DATA_VALUES_X_INDEX, Base::DEBUG, Base::DEFAULT_MARGIN, Base::DEFAULT_TARGET_WIDTH, Base::LABEL_MARGIN, Base::LEGEND_MARGIN, Base::THOUSAND_SEPARATOR

Instance Attribute Summary collapse

Attributes inherited from Base

#additional_line_values, #bottom_margin, #center_labels_over_point, #colors, #font, #font_color, #has_left_labels, #hide_legend, #hide_line_markers, #hide_line_numbers, #hide_title, #labels, #left_margin, #legend_box_size, #legend_font_size, #legend_margin, #marker_color, #marker_count, #marker_font_size, #maximum_value, #minimum_value, #no_data_message, #right_margin, #sort, #stacked, #title, #title_font_size, #title_margin, #top_margin, #x_axis_label, #y_axis_increment, #y_axis_label

Instance Method Summary collapse

Methods inherited from Base

#add_color, #data, #initialize, #margins=, #replace_colors, #theme=, #theme_37signals, #theme_greyscale, #theme_keynote, #theme_odeo, #theme_pastel, #theme_rails_keynote, #to_blob, #write

Methods included from Deprecated

#graph_height, #graph_left, #graph_top, #graph_width, #scale_measurements, #total_height

Constructor Details

This class inherits a constructor from Gruff::Base

Instance Attribute Details

#hide_labels_less_than ⇒ Object

Do not show labels for slices that are less than this percent. Use 0 to always show all labels. Defaults to 0



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# File 'lib/gruff/pie.rb', line 23

def hide_labels_less_than
  @hide_labels_less_than
end

#zero_degree ⇒ Object

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.



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# File 'lib/gruff/pie.rb', line 20

def zero_degree
  @zero_degree
end

Instance Method Details

#draw ⇒ Object 



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# File 'lib/gruff/pie.rb', line 31

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
      
      label_val = ((data_row[DATA_VALUES_INDEX].first / total_sum) * 100.0).round
      unless label_val < @hide_labels_less_than
        # End the string with %% to escape the single %.
        # RMagick must use sprintf with the string and % has special significance.
        label_string = label_val.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

#initialize_ivars ⇒ Object 



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# File 'lib/gruff/pie.rb', line 25

def initialize_ivars
  super
  @zero_degree = 0.0
  @hide_labels_less_than = 0.0
end