重心法选址

2单设施重心法选址

2.1实验目的

掌握单设施重心法选址的原理，能够计算简单选址题目中待选设施的位置； 掌握单设施重心选址的算法流程，能够设计类似题目的算法流程，并编写程序。 2.2实验过程

(1)单设施重心法选址的原理

重心法选址模型示意图如图2-1所示。

Y?X图2-1 单设施重心法选址选址示意图

求解目标：C-总成本最低

n MinC?fiVidi i?1

其中：fi-序号为i的点的运输费率； Vi-序号为i的点的产量或者销量；

di-序号为i的点到待选设施点的相对距离。

待选设施位置的计算公式： nn(fiViyi/di) (fiVixi/di)i?1 i?1Y?cXc?nn (fV/diii)(fV/d)iii i?1i?1

其中：Xc-重心的X坐标； Yc-重心的Y坐标； Xi-第i个地点X坐标； Yi-第i个地点Y坐标；

22di?(X?d)?(Yc?diy)cix

?????

(2)算法流程图，如图2-2所示。

初始化 Xc=0，Yc=0JD=0.001

赋值 SumCOld = 0SumCNew = 0 Sum1 = 0Sum2 = 0 Sum3 = 0 计算di SumCOldj=j+1Xc,Yc DiSumCNew 否 判断（SumCOld-SumCNew）<=JD

是

输出 Xc,YcSumCNew j(跌代次数)

停止

图2-2 算法流程图

2.3实验结果

（1）单设施重心法选址程序参数设定及其求解界面如图2-3所示。

图2-3 单设施重心法选址程序参数设定及其求解界面

（2）参数设定及其求解界面变量声明部分（代码） Private Sub Command1_Click() If Text1.Text = \

MsgBox \横坐标不允许为空\ Text1.SetFocus Exit Sub

ElseIf IsNumeric(Text1.Text) = False Then MsgBox \横坐标必须为数值型数据！\ Text1.Text = \ Text1.SetFocus Exit Sub End If

If Text2.Text = \

MsgBox \纵坐标不允许为空\ Text2.SetFocus Exit Sub

ElseIf IsNumeric(Text2.Text) = False Then MsgBox \纵坐标必须为数值型数据！\ Text2.Text = \ Text2.SetFocus Exit Sub End If

If Text3.Text = \

MsgBox \产量或销量不允许为空\ Text3.SetFocus Exit Sub

ElseIf IsNumeric(Text3.Text) = False Then MsgBox \产量或销量应为数值型数据！\ Text3.Text = \ Text3.SetFocus Exit Sub

ElseIf Val(Text3.Text) < 0 Then

MsgBox \产量或销量应为正数，否则无实际意义！\ Text3.Text = \ Text3.SetFocus Exit Sub End If

If Text4.Text = \

MsgBox \运输费率不允许为空\ Text4.SetFocus Exit Sub

ElseIf IsNumeric(Text4.Text) = False Then MsgBox \运输费率应为数值型数据！\ Text4.Text = \ Text4.SetFocus Exit Sub

ElseIf Val(Text4.Text) < 0 Then

MsgBox \运输费率应为正数，否则无实际意义！\ Text4.Text = \ Text4.SetFocus Exit Sub End If

If Text5.Text = \

MsgBox \横坐标不允许为空\ Text5.SetFocus Exit Sub

ElseIf IsNumeric(Text5.Text) = False Then MsgBox \横坐标必须为数值型数据！\ Text5.Text = \ Text5.SetFocus Exit Sub End If

If Text6.Text = \

MsgBox \纵坐标不允许为空\ Text6.SetFocus Exit Sub

ElseIf IsNumeric(Text6.Text) = False Then MsgBox \纵坐标必须为数值型数据！\ Text6.Text = \ Text6.SetFocus Exit Sub End If

If Text7.Text = \ MsgBox \精度不允许为空\ Text7.SetFocus Exit Sub

ElseIf IsNumeric(Text7.Text) = False Then MsgBox \精度应为数值型数据！\ Text7.Text = \ Text7.SetFocus Exit Sub

ElseIf Val(Text7.Text) < 0 Then

MsgBox \精度应为正数，否则无实际意义！\ Text7.Text = \ Text7.SetFocus Exit Sub End If

For i = 1 To List1.ListCount

If Text1.Text = Val(List1.List(i - 1)) And Text2.Text = Val(List2.List(i - 1)) Then

MsgBox \与第\输入坐标值相同，请重新输入\ Text1.Text = \ Text2.Text = \ Text3.Text = \ Text4.Text = \ Text1.SetFocus Exit Sub End If Next i

List1.AddItem Text1.Text List2.AddItem Text2.Text List3.AddItem Text3.Text List4.AddItem Text4.Text Text1.Text = \ Text2.Text = \ Text3.Text = \ Text4.Text = \ Text1.SetFocus

If List1.ListCount >= 2 Then Command2.Enabled = True End If End Sub

Private Sub Command2_Click() Xc = Val(Text5.Text) Yc = Val(Text6.Text) JD = Val(Text7.Text)

Dim SumCO As Double Dim SumCN As Double Dim Sum1 As Double Dim Sum2 As Double Dim Sum3 As Double

For j = 1 To 10000