gistfile1.rb

#!/usr/bin/ruby

require "gnuplot"
require "integration"

def draw_plot

  Gnuplot.open do |gp|
    Gnuplot::Plot.new( gp ) do |plot|

      plot.xrange "[-10:10]"
      string = ""
      for i in 1..6 do
        string += (nth_fourier i).to_s + " "
        p nth_fourier i
      end
      plot.title  sting
      plot.xlabel "x"
      plot.ylabel "y"

      # x = (1..6).collect { |v| v.to_f }
      # y = x.collect { |v| nth_fourier v }
      x = [-3.14, 0, 0, 3.14]
      y = [-1, -1, 1, 1]
      plot.data = [

        #String function
        Gnuplot::DataSet.new( "1.273*sin(x)+0.424*sin(3*x)+0.255*sin(5*x)" ) { |ds|
          ds.with = "lines"
          ds.title = "String function"
          ds.linewidth = 4
        },

        #Points
        Gnuplot::DataSet.new( [x, y] ) { |ds|
          ds.with = "linespoints"
          ds.title = "Array data"
        }
      ]

    end
  end
end

def nth_fourier n

  i = -(Math::PI)
  b = 0.0

  while i < 0
   b += 0.01 * (-1) * Math.sin(n * i)
   i += 0.01
  end

  while i < Math::PI
   b += 0.01 * Math.sin(n * i)
   i += 0.01
  end
  b = b*2/(2*Math::PI)

end

draw_plot