问题
I am new to the VBA programming and have written a VBA function for interpolation. I attempt to get the input from cell C17 and other cell in column Cto the function "WindPressure"
The function then gets the input from column C( Height above ground z (m) ) and interpolate to get the design wind pressure, but I fail due to the circular error.
The code is as follow:
Function WindPressure(z As Double) As Double
Dim Row_Nos As Integer
Dim x1 As Double
Dim x2 As Double
Dim x3 As Double
Dim y1 As Double
Dim y2 As Double
Dim y3 As Double
' Select first line of data.
Range("T13").Select
' Set Nos of row to interploate
Row_Nos = 12
' Interpolation for Design Wind pressure
For i = 0 To Row_Nos
' Case 1: <= 5m
If i = 0 And z <= ActiveCell.Value Then
WindPressure = ActiveCell.Offset(0, 1).Value
' Shifting Back
ActiveCell.Offset(0, -1).Select
'Exit If Enter this if statement
Exit Function
ElseIf i >= 0 And z <= ActiveCell.Value Then
' Case 2: > 5m
x1 = z
x2 = ActiveCell.Offset(-1, 0).Value
x3 = ActiveCell.Offset(2, 0).Value
y2 = ActiveCell.Offset(-2, 1).Value
y3 = ActiveCell.Offset(2, 0).Value
y1 = ((x1 - x3) / (x2 - x3) * (y2 - y3)) + y3
WindPressure = y1
' Shifting Back
ActiveCell.Offset(-1, -1).Select
'Exit If Enter this if statement
Exit Function
End If
ActiveCell.Offset(1, 0).Select
Next i
End Function
- Could anyone tell me which step in my script is wrong
- Is there anyway convenient to test a function? As it is not like a procedure which execute directly by clicking the F5 button
Many thanks for your attention and help.
回答1:
This is how to debug it with F5 or F8 as a procedure:
Public Sub TestMe()
Debug.Print windpressure(7)
End Sub
Function windpressure(z As Double) As Double
Stop
'the rest of the function
' Dim Row_Nos As Integer
' Dim x1 As Double
' Dim x2 As Double
' Dim x3 As Double
End Function
Now run TestMe by pressing F8 and enjoy the debugging.
Another way is to write ?WindPressure(7) in the immediate window and to put a stop sign in the VB Editor. It will go line by line.
Concerning the errors, remove the Select part from the function, VBA does not allow you to use it there.
回答2:
As @YowE3K has pointed out, debugging doesn't help when the function tries to modify the environment.
So, your code tries to select range T13 which it can't do in a UDF. After this any reference to the ActiveCell is wrong and trying to change the active cell fails as you can't modify the environment.
On a side note, you also haven't put Option Explicit at the top of the module otherwise it would also complain you haven't declared the variable i.
So, rather than change the ActiveCell just set a reference to the cell you need. Whenever you use ActiveCell use that range reference instead.
Option Explicit
Function WindPressure(z As Double) As Double
Dim Row_Nos As Integer
Dim x1 As Double
Dim x2 As Double
Dim x3 As Double
Dim y1 As Double
Dim y2 As Double
Dim y3 As Double
Dim i As Long
Dim rT13 As Range
' Select first line of data.
'Range("T13").Select '**** Won't work in a UDF ****
Set rT13 = Range("T13") 'Set a reference to T13 instead.
' Set Nos of row to interploate
Row_Nos = 12
' Interpolation for Design Wind pressure
For i = 0 To Row_Nos
' Case 1: <= 5m
If i = 0 And z <= rT13.Value Then
WindPressure = rT13.Offset(0, 1).Value
'Exit If Enter this if statement
Exit Function
ElseIf i >= 0 And z <= rT13.Value Then
' Case 2: > 5m
x1 = z
x2 = rT13.Offset(-1, 0).Value
x3 = rT13.Offset(2, 0).Value
y2 = rT13.Offset(-2, 1).Value
y3 = rT13.Offset(2, 0).Value
y1 = ((x1 - x3) / (x2 - x3) * (y2 - y3)) + y3
WindPressure = y1
'Exit If Enter this if statement
Exit Function
End If
Next i
End Function
To check your code you could put a break-point on Range("T13").Select and add a watch on ActiveCell.Address - when the code reaches the line you'll see that the ActiveCell remains the cell that you typed the formula into.
来源：https://stackoverflow.com/questions/46171685/circular-error-in-vba-user-defined-function