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.
# 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 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 # 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
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