Ruby実用例 〜スプライン補間〜 のバックアップソース(No.2)

• バックアップ一覧
• 差分 を表示
• 現在との差分 を表示
• バックアップ を表示
• Ruby実用例 〜スプライン補間〜 へ行く。
  • 1 (2005-11-08 11:23:06 (火))
  • 2 (2005-11-08 11:48:32 (火))
  • 3 (2005-11-08 11:52:15 (火))

** spline.rb [#cb602618]

 class Spline
   
   # 初期化．3次スプライン補間曲線を求める
   def initialize(x, y)
     @x = x
     @y = y
     @z = []
     
     n = @x.length
     h = []
     d = []
     @z[0] = @z[n-1] = 0
     
     for i in 0...n-1
       h[i  ] =  @x[i+1] - @x[i]
       d[i+1] = (@y[i+1] - @y[i]) / h[i]
     end
     
     @z[1] = d[2] - d[1] - h[0] * @z[0]
     d[1] = 2 * (@x[2] - @x[0])
     
     for i in 1...n-2
       t = h[i] / d[i]
       @z[i+1] = d[i+2] - d[i+1] - @z[i] * t
       d[i+1] = 2 * (@x[i+2] - @x[i]) - h[i] * t
     end
     
     @z[n-2] -= h[n-2] * @z[n-1]
     
     i = n - 2
     while i > 0
       @z[i] = (@z[i] - h[i] * @z[i+1]) / d[i]
       i -= 1
     end
     
   end
   
   # 補間値を返すメソッド
   def interpolate(t)
     i = 0
     j = @x.length - 1
     
     while i < j
       k = (i + j) / 2
       if (@x[k] < t)
         i = k + 1
       else
         j = k
       end
     end
     
     if i > 0
       i -= 1
     end
     
     h = @x[i+1] - @x[i]
     d = t - @x[i]
     return (((@z[i+1] - @z[i]) * d / h + @z[i] * 3) * d + ((@y[i+1] - @y[i]) / h - (@z[i] * 2 + @z[i+1]) * h)) * d + @y[i]
     
   end
   
 end

** getSpline.rb [#t7a61856]

 #!/usr/bin/env ruby
 
 org_path = File::dirname(__FILE__)
 $:.unshift(org_path.untaint)
 require 'spline'
 
 x = [1, 2, 3, 4, 5]
 y = [2.0, 1.1, 2.4, 3.2, 5.9]
 
 curve = Spline.new(x, y)
 
 i = 1.0
 while i <= 5.0
   printf("%f,%f\r\n", i, curve.interpolate(i))
   i += 0.1
 end


* 結果 [#xc7e161d]

#ref(fig1.png,nolink)
#ref(fig2.png,nolink)
#ref(fig3.png,nolink)