物流管理單設施選址（single   facility   location）   
  這是一個根據不同到工廠運輸量、運輸費率、位置求解最佳倉庫位置的問題。   
  下邊是我用VB寫的代碼（僅供參考）   
  '外部接口變量   
  Public   V(),   R(),   X(),   Y()   As   Double   
  'V()   運輸量   
  'R()   運輸費率   
  'X,Y   地點的相對位置   
  Public   n   As   Integer   
  'n表示倉庫數量   
  '內部函數變量   
  Public   X1,   Y1,   SX1,   SX2,   SY1,   SY2,   D(),   Cxy   As   Double   
  Public   flagcheck   As   Boolean   
  '初始化過程   
  Sub   init()   
  Dim   i   As   Integer   
    SX1   =   0   
    SX2   =   0   
    SY1   =   0   
    SY2   =   0   
    For   i   =   0   To   n   -   1   
      SX1   =   SX1   +   V(i)   *   R(i)   *   X(i)   
      SX2   =   SX2   +   V(i)   *   R(i)   
      SY1   =   SY1   +   V(i)   *   R(i)   *   Y(i)   
      SY2   =   SY2   +   V(i)   *   R(i)   
    Next   
      X1   =   SX1   /   SX2   
      Y1   =   SY1   /   SY2   
      
  End   Sub   
  '求解倉庫的最佳位置   
  Function   slove()   As   Integer   
    Dim   flag   As   Boolean   
    Dim   i,   re   As   Integer   
    Dim   TempX,   TempY   As   Double   
    Dim   intRValue   As   Integer   
    intRValue   =   1   
    Call   init   
    If   n   =   1   Then   
      re   =   MsgBox("只有一個地點",   vbOKOnly)   
    Else   
    Do   
      
      TempX   =   X1   
      TempY   =   Y1   
    For   i   =   0   To   n   -   1   
      D(i)   =   Sqr((X(i)   -   X1)   *   (X(i)   -   X1)   +   (Y(i)   -   Y1)   *   (Y(i)   -   Y1))   
      If   D(i)   =   0   Then   
        D(i)   =   1   
      End   If   
    Next   
      
      SX1   =   0   
      SX2   =   0   
      SY1   =   0   
      SY2   =   0   
      For   i   =   0   To   n   -   1   
        SX1   =   SX1   +   V(i)   *   R(i)   *   X(i)   /   D(i)   
        SX2   =   SX2   +   V(i)   *   R(i)   /   D(i)   
        SY1   =   SY1   +   V(i)   *   R(i)   *   Y(i)   /   D(i)   
        SY2   =   SY2   +   V(i)   *   R(i)   /   D(i)   
      Next   
        X1   =   SX1   /   SX2   
        Y1   =   SY1   /   SY2   
      
      intRValue   =   intRValue   +   1   
    Loop   While   (Abs(X1   -   TempX)   <=   Cxy   And   Abs(Y1   -   TempY)   <=   Cxy)   =   False   
    End   If   
  slove   =   intRValue   
  End   Function   
  '求解的最小費率函數   
  Function   FindMinTc()   As   Double   
    Dim   TC   As   Double   
    Dim   i   As   Integer   
    For   i   =   0   To   n   -   1   
      D(i)   =   Sqr((X(i)   -   X1)   *   (X(i)   -   X1)   +   (Y(i)   -   Y1)   *   (Y(i)   -   Y1))   
    
    Next   
    TC   =   0   
    For   i   =   0   To   n   -   1   
      TC   =   TC   +   V(i)   *   R(i)   *   D(i)   
    Next   
    FindMinTc   =   TC   
  End   Function