atan2.txt

描述：matlab的Atan2函数与vb.net的Atan2函数计算结果并不一致。该程序用vb.net实现了matlab的Atan2函数。

 描述：matlab的Atan2函数与vb.net的Atan2函数计算结果并不一致。该程序用vb.net实现了matlab的Atan2函数。
Function Atan2 in matlab is different from that in vb.net. The program use vb.net to realize Atan2 function in matlab.

'y is the imaginary part of a complex and x is the real part
    Public Shared Function matlab_Atan2(ByVal y As Double, ByVal x As Double) As Double
        Dim value As Double
        Dim m As Integer = 2 * Math.Sign(x) + Math.Sign(y)

        If x = 0 AndAlso y = 0 Then
            Return 0
        End If

        If y = 0 AndAlso x <> 0 Then
            If x > 0 Then
                Return 0
            Else
                Return -Math.PI
            End If

        End If

        If x = 0 AndAlso y <> 0 Then
            If y > 0 Then
                Return Math.PI / 2
            Else
                Return -1 * Math.PI / 2
            End If
        End If

        value = Math.Atan(y / x)

        Select Case m
            Case 3      'sign(x,y)=(+,+)
                Return value
            Case -3          'sign(x,y)=(-,-)
                Return value - Math.PI
            Case 1      'sign(x,y)=(+,-)
                Return value
            Case Else  'case -1   'sign(x,y)=(-,+)
                Return value + Math.PI
        End Select

    End Function