PDF::Writer：PDF::Charts::StdDev#label, #label=

require 'pdf/charts/stddev'

pdf = PDF::Writer.new

chart = PDF::Charts::StdDev.new

p chart.label
chart.label = PDF::Charts::StdDev::Label.new do |label|
  label.height            = 25
  label.background_color  = Color::RGB::Blue
  label.text_color        = Color::RGB::White
  label.text_size         = 12
end

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

pdf.save_as("2008042800.pdf")

で、

#<PDF::Charts::StdDev::Label:0x4038760c @text_size=12, @text_color=#<Color::RGB:0x40261bec @b=1.0, @g=1.0, @r=1.0>, @background_color=#<Color::RGB:0x4026830c @b=0.0, @g=0.0, @r=0.0>, @height=25>