Question

我正在尝试使用Excel VB实现一个简单的Newton方法迭代求解器（我从未使用过VB。）

我一直收到错误loop without a Do，我无法弄清楚我在这里做错了什么。

我正在尝试找到函数z^3 - z^2 - (B^2 + B - A)z - A*B的根，称为压缩因子。

我的来源MSN

Function zCalculation(ByVal temp As Double, ByVal press As Double) As Double

Dim tempCr As Double
Dim pressCr As Double
Dim A As Double
Dim B As Double

tempCr = temp / 238.5

pressCr = press / 547.424092

A = pressCr / tempCr
A = A / (9 * (2 ^ (1 / 3) - 1))
B = pressCr / tempCr
B = B * (2 ^ (1 / 3) - 1) / 3



Dim zNot As Double
Dim counter As Integer
counter = 0
zNot = 1#

Do
    counter = counter + 1

    zNot = zNot - (zNot ^ 3 - zNot ^ 2 - (B ^ 2 + B - A) * zNot - A * B) / (3 * zNot ^ 2 - 2 * zNot - (B ^ 2 + B - A))
    If counter > 1000 Then
       Exit Do

Loop Until eval(zNot, A, B) < 0.000001


zCalculation = zNot


End Function

断裂

Function eval(ByVal z As Double, ByVal A As Double, ByVal B As Double) As Double

    eval = z ^ 3 - z ^ 2 - (B ^ 2 + B - A) * z - A * B

End Function

Answer 1

你需要一个：

End If

代码。

Answer 2

您可以尝试：

 Function zCalculation(ByVal temp As Double, ByVal press As Double) As Double

  Dim tempCr As Double
  Dim pressCr As Double
  Dim A As Double
  Dim B As Double

  tempCr = temp / 238.5

  pressCr = press / 0.546789

  A = pressCr / tempCr
  A = A / (9 * (2 ^ (1 / 3) - 1))
  B = pressCr / tempCr
  B = B * (2 ^ (1 / 3) - 1) / 3



  Dim zNot As Double
  Dim counter As Integer
  counter = 0
  zNot = 1#

  Do
      counter = counter + 1

      zNot = zNot - (zNot ^ 3 + zNot ^ 2 - (B ^ 2 + B - A) * zNot - A * B) / (3 * zNot ^ 2 + 2 * zNot - (B ^ 2 + B - A))
      If counter > 1000 Then
         Exit Do
      End if  ' <--- Here

  Loop Until eval(zNot, A, B) < 0.000001

  zCalculation = zNot
 End Function

Answer 3

Sub datacalculationsandformat()
Dim row As Integer
row = 2
Do While Cells(row, 2) <> ""
Cells(row, 3).Value = Cells(row, 2).Value * 0.3
Cells(row, 4).Value = Cells(row, 2) * 0.1
Cells(row, 5).Value = Cells(row, 2).Value + Cells(row, 3).Value + Cells(row, 4).Value
If Cells(row, 5).Value >= 8000 Then
Worksheets("Sheet1").Cells(row, 5).Font.Bold = True
row = row + 1
Loop

循环没有Do错误

3 个答案: