Does VBA have an ATan2 function?

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独厮守ぢ
独厮守ぢ 2021-01-20 00:27

I\'d like to calculate atan2 in VBA, but I\'m not sure if that function exists (or even where to find a canonical list of built-in VBA functions). I\'m not usi

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  • 2021-01-20 00:55

    As pointed out by MarkJ earlier, the above code will fail when X < 0 and y=0. I believe the following will work all the time:

    Function ArcTan2(X As Double, Y As Double) As Double
    
    Private Const PI As Double = 3.14159265358979
    Private Const PI_2 As Double = 1.5707963267949
    
        Select Case X
            Case Is > 0
                ArcTan2 = Atn(Y / X)
            Case Is < 0
                ArcTan2 = Atn(Y / X) + PI * Sgn(Y)
                If Y = 0 Then ArcTan2 = ArcTan2 + PI
            Case Is = 0
                ArcTan2 = PI_2 * Sgn(Y)
        End Select
    
    End Function
    

    It takes advantage of Sgn(0) returning 0 in the case where both x and y are 0.

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  • 2021-01-20 01:02

    To get a list, type into your module

    VBA.Math
    

    Or use the object browser. You will find Atn and Tan, amongst others, but the list is quite short and ATan2 is not included.

    If you wish to add a reference to an Excel library, you can use:

    Excel.WorksheetFunction.Atan2
    

    EDIT: You can call Excel worksheet functions from any Office application that allows you to add a reference to the Excel libraries. This does not mean using Excel or a worksheet, just the function.

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  • 2021-01-20 01:09

    You can try with

    Application.Atan2
    
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  • 2021-01-20 01:14

    Maybe this code would suit you:

    Private Const Pi As Double = 3.14159265358979
    
    Public Function Atn2(y As Double, x As Double) As Double
    
      If x > 0 Then
    
        Atn2 = Atn(y / x)
    
      ElseIf x < 0 Then
    
        Atn2 = Sgn(y) * (Pi - Atn(Abs(y / x)))
    
      ElseIf y = 0 Then
    
        Atn2 = 0
    
      Else
    
        Atn2 = Sgn(y) * Pi / 2
    
      End If
    
    End Function
    
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