Ruby実用例 〜スプライン補間〜 のバックアップ(No.1)

• バックアップ一覧
• 差分 を表示
• 現在との差分 を表示
• ソース 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))

class Spline

 # 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
 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