PDF::Writer：PDF::Charts::StdDev#inner_borders, #inner_borders=, #outer_borders, #outer_borders=

require 'pdf/charts/stddev'

pdf = PDF::Writer.new

chart = PDF::Charts::StdDev.new

p chart.inner_borders
p chart.outer_borders

chart.data << PDF::Charts::StdDev::DataPoint.new(1, 4.0000, 0.5774)
chart.render_on pdf

pdf.save_as("2008042900.pdf")

で、

nil
#<PDF::Charts::StdDev::Marker:0x40387c4c @color=#<Color::RGB:0x40268690 @b=0.0, @g=0.0, @r=0.0>, @style=#<PDF::Writer::StrokeStyle:0x40387be8 @width=1.5, @dash=nil, @join=nil, @cap=nil, @miter_limit=nil>>

require 'pdf/charts/stddev'

pdf = PDF::Writer.new

chart = PDF::Charts::StdDev.new

chart.outer_borders = PDF::Charts::StdDev::Marker.new do |marker|
  marker.style = PDF::Writer::StrokeStyle.new(1.5)
  marker.color = Color::RGB::Blue
end

chart.data << PDF::Charts::StdDev::DataPoint.new(1, 4.0000, 0.5774)
chart.render_on pdf

pdf.save_as("2008042901.pdf")

require 'pdf/charts/stddev'

pdf = PDF::Writer.new

chart = PDF::Charts::StdDev.new

chart.inner_borders = PDF::Charts::StdDev::Marker.new do |marker|
  marker.style = PDF::Writer::StrokeStyle.new(1.5)
  marker.color = Color::RGB::Blue
end
chart.outer_borders = nil

chart.data << PDF::Charts::StdDev::DataPoint.new(1, 4.0000, 0.5774)
chart.render_on pdf

pdf.save_as("2008042902.pdf")

inner_borders ってどこ？