没有这方面的经历，在网上找了段代码，可以运行，拟合的是二次曲线。
新建一工程，窗口上放4个按钮，从command1到command4分别是“画坐标、采样点生成、曲线拟合、退出”，复制下列代码并运行即可看到效果。
Option Explicit
Dim x() As Double, y() As Double
Dim A(20, 20) As Double, M As Double, B() As Double '最多取20次的拟合
Dim N As Double, I As Double, j As Double
Dim xiaoA() As Double
Dim Xmin As Double, Xmax As Double
Dim Ymin As Double, Ymax As Double
Dim X0pos As Double, Y0pos As Double
Dim xmaxpos As Double, ymaxpos As Double
Dim xstep As Double, ystep As Double
Dim xl As Double, yl As Double
Dim xbc As Double, ybc As Double
Dim bc As Double
Dim Xh As Double
Private Sub HuaZuoBiao(x() As Double, y() As Double)
ReDim xpos(I) As Double
ReDim ypos(I) As Double
ReDim x(I), y(I)
X0pos = Width * 0.25 '坐标原点最左点
Y0pos = Height * 0.75 '坐标原点最低点
xmaxpos = Width * 0.85 '坐标最右点
ymaxpos = Height * 0.15 '坐标最高点
xstep = (xmaxpos - X0pos) / (Xmax - Xmin) '对应X轴上单位长度代表的屏幕宽度值
ystep = (ymaxpos - Y0pos) / (Ymax - Ymin) '对应Y轴上单位长度代表的屏幕高度值
'在屏幕上画直角坐标系
ForeColor = vbBlue
Line (Width * 0.1, Y0pos)-(Width * 0.9, Y0pos) '画X坐标轴,从左10%，到右的90%处
Line (X0pos, Height * 0.1)-(X0pos, Height * 0.9) '画y坐标轴,从上10%，到下的90%处
Font.Size = 20 '指定X轴，Y轴标志的字体大小
CurrentX = Width * 0.9
CurrentY = Y0pos + 100
Print "X" '在横线上画X轴标志
'在横线上画X轴箭头标志
CurrentX = Width * 0.9
CurrentY = Y0pos
Line (CurrentX - 200, CurrentY - 50)-(CurrentX, CurrentY)
Line (CurrentX, CurrentY)-(CurrentX - 200, CurrentY + 50)
CurrentX = X0pos - 500
CurrentY = Height * 0.1
Print "y" '在纵线上画Y轴标志
'在纵线上画Y轴箭头标志
CurrentX = X0pos
CurrentY = Height * 0.1
Line (CurrentX - 50, CurrentY + 200)-(CurrentX, CurrentY)
Line (CurrentX, CurrentY)-(CurrentX + 50, CurrentY + 200)
CurrentX = X0pos + 200 '此为Y轴左边500绝对坐标处
CurrentY = Y0pos + 400 '取当前Y轴上的相对坐标值
Print "f=f(x)" '在Y轴左边500绝对坐标处对应显示Y轴相对坐标刻度值
xl = Xmax - Xmin
yl = Ymax - Ymin
If xl < 0.01 Then
xbc = 0.001
ElseIf xl <= 0.1 Then
xbc = 0.01
ElseIf xl <= 2 Then
xbc = 0.1
ElseIf xl <= 20 Then
xbc = 1
ElseIf xl <= 120 Then
xbc = 10
ElseIf xl <= 1000 Then
xbc = 100
ElseIf xl <= 10000 Then
xbc = 1000
Else
xbc = 10000
End If
If yl < 0.01 Then
ybc = 0.001
ElseIf yl <= 0.1 Then
ybc = 0.01
ElseIf yl <= 2 Then
ybc = 0.1
ElseIf yl <= 20 Then
ybc = 1
ElseIf yl <= 120 Then
ybc = 10
ElseIf yl <= 1000 Then
ybc = 100
ElseIf yl <= 10000 Then
ybc = 1000
Else
ybc = 10000
End If
For bc = Xmin To Xmax Step xbc
If bc <= Xmax Then
x(j) = bc 'X轴上的相对坐标值
xpos(j) = X0pos + (x(j) - Xmin) * xstep
Line (xpos(j), Y0pos)-(xpos(j), ymaxpos), vbRed ' 画垂直于X轴的刻度线，只画了100个绝对尺寸
Else
End If
Font.Size = 10 '指定X轴，Y轴坐标刻度值的字体大小
CurrentX = xpos(j) - 200 '取当前X轴上的相对坐标值
CurrentY = Y0pos + 100 '此为X轴下方100绝对坐标处
Print x(j) '在X轴下方100绝对坐标处对应显示X轴相对坐标刻度值
Next bc
For bc = Ymin To Ymax Step ybc
If bc <= Ymax Then
y(j) = bc 'X轴上的相对坐标值
ypos(j) = Y0pos + (y(j) - Ymin) * ystep
Line (X0pos, ypos(j))-(xmaxpos, ypos(j)), vbRed ' 画垂直于X轴的刻度线，只画了100个绝对尺寸
Else
End If
Font.Size = 10 '指定X轴，Y轴坐标刻度值的字体大小
CurrentX = X0pos - 500 '取当前X轴上的相对坐标值
CurrentY = ypos(j) - 100 '此为X轴下方100绝对坐标处
Print y(j) '在X轴下方100绝对坐标处对应显示X轴相对坐标刻度值
Next bc
End Sub
Private Sub ZuoDian(x() As Double, y() As Double)
ReDim xpos(I) As Double
ReDim ypos(I) As Double
For I = 0 To N
xpos(I) = X0pos + (x(I) - Xmin) * xstep
ypos(I) = Y0pos + (y(I) - Ymin) * ystep
If y(I) <= Ymax Then
DrawWidth = 4
PSet (xpos(I), ypos(I)), vbRed
Else
End If
Next I
DrawWidth = 1
End Sub
Private Sub HuaQuXian(xiaoA() As Double)
ReDim xpos(I) As Double
ReDim ypos(I) As Double
Dim Ysum As Double, Ii As Double
For Ii = Xmin To Xmax Step 1 / (Xmax - Xmin)
Ysum = 0
For j = 1 To M
Ysum = Ysum + xiaoA(j) * Ii ^ (j - 1)
Next j
xpos(I) = X0pos + (Ii - Xmin) * xstep
ypos(I) = Y0pos + (Ysum - Ymin) * ystep
DrawWidth = 2
If Ii = Xmin Then
xpos(0) = X0pos + (Ii - Xmin) * xstep
ypos(0) = Y0pos + (Ysum - Ymin) * ystep
PSet (xpos(0), ypos(0))
Else
End If
If Ysum <= Ymax Then
DrawWidth = 2
Line -(xpos(I), ypos(I)), vbBlue
Else
End If
Next Ii
DrawWidth = 1
End Sub
Private Sub JieFangCheng(A() As Double, B() As Double, x() As Double)
Dim nn As Double
nn = UBound(B)
Dim TempA As Double, L As Double, K As Double, Kk As Double
Dim Ii As Double, ChuShu As Double, Sum As Double
For I = 1 To nn
L = 0: Kk = 0
For j = I To nn
If A(j, I) = 0 Then L = L + 1
Next j
For j = I To nn - L
If A(j, I) = 0 Then
Kk = Kk + 1
For K = I To nn
TempA = A(j, K)
A(j, K) = A(nn - Kk + 1, K)
A(nn - Kk + 1, K) = TempA
Next K
TempA = B(j): B(j) = B(nn - Kk + 1): B(nn - Kk + 1) = TempA
End If
Next j
For Ii = I To nn - L
ChuShu = A(Ii, I)
For j = I To nn
A(Ii, j) = A(Ii, j) / ChuShu
Next j
B(Ii) = B(Ii) / ChuShu
Next Ii
For Ii = I + 1 To nn - L
For j = I To nn
A(Ii, j) = A(Ii, j) - A(I, j)
Next j
B(Ii) = B(Ii) - B(I)
Next Ii
Next I
For I = 1 To nn
For j = 1 To I - 1
A(I, j) = 0
Next j
Next I
x(nn) = B(nn) / A(nn, nn)
For I = nn - 1 To 1 Step -1
Sum = 0
For j = I + 1 To nn
Sum = Sum + A(I, j) * x(j)
Next j
x(I) = (B(I) - Sum) / A(I, I)
Next I
End Sub
Private Sub Command1_Click()
Cls
Xmin = 0 ' InputBox("请输入x坐标下限值", "x坐标下限值", 0)
Ymin = 0 'InputBox("请输入y坐标下限值", "y坐标下限值", 0)
Xmax = 10 ' InputBox("请输入x坐标上限值", "x坐标上限值度", 10)
Ymax = 10 'InputBox("请输入y坐标上限值", "y坐标上限值度", 10)
N = 20
For I = 0 To N
ReDim Preserve x(I)
ReDim Preserve y(I)
Next I
Call HuaZuoBiao(x, y)
End Sub
Private Sub Command2_Click()
For I = 0 To N
x(I) = Xmin + I * (Xmax - Xmin) / N 'InputBox("请输入X坐标测量值", "X坐标值", "0") '
y(I) = Sin(x(I)) + 5 ' InputBox("请输入Y坐标测量值", "Y坐标值", "0") '
Next I
Call ZuoDian(x, y)
End Sub
Private Sub Command3_Click()
M = 20 'InputBox("请输入拟合曲线次数M", "拟合曲线", 3)
Erase B: Erase xiaoA: Erase A '必不可少***********
ReDim B(M): ReDim xiaoA(1 To M)
'形成方程组的各元素
A(1, 1) = N
For I = 1 To N
B(1) = B(1) + y(I)
Next I
For j = 2 To M
For I = 1 To N
A(1, j) = A(1, j) + x(I) ^ (j - 1)
Next I
Next j
For I = 2 To M
For j = 1 To M
For Xh = 1 To N
A(I, j) = A(I, j) + x(Xh) ^ (I + j - 2)
If j = 1 Then
B(I) = B(I) + x(Xh) ^ (I - 1) * y(Xh)
End If
Next Xh
Next j
Next I
Call JieFangCheng(A, B, xiaoA)
ForeColor = vbBlack
PSet (0, 0)
For I = 1 To M
'Print Tab(6); "a"; I - 1; Tab(12); "="; xiaoA(I);
Next I
Dim Str As String: Str = "y="
For I = 1 To M '写方程
If I < M Then
Str = Str & xiaoA(I) & "*x^" & I - 1 & "+"
Else
Str = Str & xiaoA(I) & "*x^" & I - 1
End If
Next I
Print vbCrLf; "曲线方程:"; vbCrLf & Str
Call HuaQuXian(xiaoA)
End Sub
Private Sub Command4_Click()
End
End Sub
Private Sub Form_Load()
Width = Screen.Width * 1 '取屏幕宽度的一半
'Height = Screen.Height * 0.5 '取屏幕高度的一半
Height = Screen.Width * 1 '取屏幕宽度的一半
Left = (Screen.Width - Width) / 2 '使窗体居屏幕中心
Top = (Screen.Height - Height) / 2 '使窗体居屏幕中心
End Sub
2014-03-07 08:48
