此函数为“直线-三次抛物线拟合”算法( 见西安交通大学《电机测试技术》）

这段多上的带码如何实现，求大神

Public Sub LinearAndCubicFit(X() As Single, Y() As Single, n As Integer, n1 As Integer, n2 As Integer)

'**** 此函数为“直线-三次抛物线拟合”算法( 见西安交通大学《电机测试技术》）****

Dim n∑Xi As Single
Dim n∑XiE2 As Single
Dim n∑Yi As Single
Dim n∑XiYi As Single

Dim n1∑Xi As Single
Dim n1∑Yi As Single
Dim n1∑XiE2 As Single
Dim n1∑XiYi As Single

Dim n2∑XiE2 As Single
Dim n2∑XiE3 As Single
Dim n2∑XiE4 As Single
Dim n2∑XiE5 As Single
Dim n2∑XiE6 As Single
Dim n2∑XiE2Yi As Single
Dim n2∑XiE3Yi As Single

Dim A(1 To 3, 1 To 3) As Single    '方程组“系数矩阵”
Dim C(1 To 3) As Single          '方程组“常数项向量”
Dim B() As Single
ReDim B(1 To 3) As Single          '方程组“解向量”

Dim Q_13(1 To 20) As Single       '直线-三次抛物线拟合之“残差平方和”
Dim n1∑ViE2 As Single
Dim n2∑ViE2 As Single

Dim i, j As Integer
Dim X0 As Single

For i = 1 To n
      n∑Xi = n∑Xi + X(i)
      n∑Yi = n∑Yi + Y(i)
      n∑XiYi = n∑XiYi + X(i) * Y(i)
      n∑XiE2 = n∑XiE2 + X(i) ^ 2
Next i

DoEvents
For i = n2 + 1 To n
      n1∑Xi = n1∑Xi + X(i)
      n1∑Yi = n1∑Yi + Y(i)
      n1∑XiE2 = n1∑XiE2 + X(i) ^ 2
      n1∑XiYi = n1∑XiYi + X(i) * Y(i)
Next i

DoEvents
For i = 1 To n2
      n2∑XiE2 = n2∑XiE2 + X(i) ^ 2
      n2∑XiE3 = n2∑XiE3 + X(i) ^ 3
      n2∑XiE4 = n2∑XiE4 + X(i) ^ 4
      n2∑XiE5 = n2∑XiE5 + X(i) ^ 5
      n2∑XiE6 = n2∑XiE6 + X(i) ^ 6
      n2∑XiE2Yi = n2∑XiE2Yi + X(i) ^ 2 * Y(i)
      n2∑XiE3Yi = n2∑XiE3Yi + X(i) ^ 3 * Y(i)
Next i

DoEvents
j = 1
For X0 = 0.3 To 1.1 Step 0.05
      A(1, 1) = n
      A(1, 2) = n∑Xi: A(2, 1) = A(1, 2)
      A(1, 3) = n2∑XiE3 - 3 * X0 * n2∑XiE2 - 3 * X0 ^ 2 * n1∑Xi + n1 * X0 ^ 3: A(3, 1) = A(1, 3)
      A(2, 2) = n∑XiE2
      A(2, 3) = n2∑XiE4 - 3 * X0 * n2∑XiE3 - 3 * X0 ^ 2 * n1∑XiE2 + X0 ^ 3 * n1∑Xi: A(3, 2) = A(2, 3)
      A(3, 3) = n2∑XiE6 - 6 * X0 * n2∑XiE5 + 9 * X0 ^ 2 * n2∑XiE4 + 9 * X0 ^ 4 * n1∑XiE2 - 6 * X0 ^ 5 * n1∑Xi + n1 * X0 ^ 6
      C(1) = n∑Yi
      C(2) = n∑XiYi
      C(3) = n2∑XiE3Yi - 3 * X0 * n2∑XiE2Yi - 3 * X0 ^ 2 * n1∑XiYi + X0 ^ 3 * n1∑Yi

      B = SolvingEquations(A(), C(), 3)    '调解方程组函数

      Dim ValueTemp As Single
      For i = n2 + 1 To n
         ValueTemp = Y(i) - (B(1) + B(2) * X(i) + B(3) * (X0 ^ 3 - 3 * X0 ^ 2 * X(i)))
         ValueTemp = ValueTemp ^ 2
         n1∑ViE2 = n1∑ViE2 + ValueTemp
      Next i

      For i = 1 To n2
         ValueTemp = Y(i) - (B(1) + B(2) * X(i) + B(3) * (X(i) ^ 3 - 3 * X0 * X(i) ^ 2))
         ValueTemp = ValueTemp ^ 2
         n2∑ViE2 = n2∑ViE2 + ValueTemp
      Next i

      Q_13(j) = n1∑ViE2 + n2∑ViE2
      If Q_13(1) >= Q_13(j) Then
         Q_13(1) = Q_13(j)
         P_X0 = X0
         AA(0) = B(1) + B(3) * P_X0 ^ 3
         AA(1) = B(2) - 3 * B(3) * P_X0 ^ 2
         BB(0) = B(1)
         BB(1) = B(2)
         BB(2) = -3 * B(3) * P_X0
         BB(3) = B(3)
   End If

   j = j + 1
   n1∑ViE2 = 0: n2∑ViE2 = 0
Next X0

P_QLineCurve = Q_13(1)

End Sub