VBA POISSON Law Function

[T111]

I need to get this function out of excel and into ASP.Net(VB). Anyone know how to do it?
Thanks,
T111!

 

[HughLerwill]

I'll guess you'll need to create an Excel Application object within the vb code and then use something like;

xlObj.WorksheetFunction.Poisson(arg1,arg2,arg3)

 

[T111]

Yes as you said I made a reference to the excel COM object. Then I could access all excels functions
e.g.

Dim objExcel As New Excel.Application
Dim result As Double
result = objExcel.Application.Poisson(0, 0.05, True)

I should of thinking of that!
Thanks!

 

[T111]

I needed to eliminate excel so here is the function in case anyone else needs it! I found it on some website in VB 6 its updated to .NET

Imports Microsoft.VisualBasic
Imports System.Math

Public Class GlobalPoisson

    Public Function IncompleteGammaC(ByVal a As Double, _
         ByVal x As Double) As Double
        Dim result As Double
        Dim IGammaEpsilon As Double
        Dim IGammaBigNumber As Double
        Dim IGammaBigNumberInv As Double
        Dim ans As Double
        Dim ax As Double
        Dim c As Double
        Dim yc As Double
        Dim r As Double
        Dim t As Double
        Dim y As Double
        Dim z As Double
        Dim pk As Double
        Dim pkm1 As Double
        Dim pkm2 As Double
        Dim qk As Double
        Dim qkm1 As Double
        Dim qkm2 As Double
        Dim Tmp As Double

        IGammaEpsilon = 0.000000000000001
        IGammaBigNumber = 4.5035996273705E+15
        IGammaBigNumberInv = 2.22044604925031 * 0.0000000000000001
        If x <= 0.0# Or a <= 0.0# Then
            result = 1.0#
            IncompleteGammaC = result
            Exit Function
        End If
        If x < 1.0# Or x < a Then
            result = 1.0# - IncompleteGamma(a, x)
            IncompleteGammaC = result
            Exit Function
        End If
        ax = a * Log(x) - x - LnGamma(a, Tmp)
        If ax < -709.782712893384 Then
            result = 0.0#
            IncompleteGammaC = result
            Exit Function
        End If
        ax = Exp(ax)
        y = 1.0# - a
        z = x + y + 1.0#
        c = 0.0#
        pkm2 = 1.0#
        qkm2 = x
        pkm1 = x + 1.0#
        qkm1 = z * x
        ans = pkm1 / qkm1
        Do
            c = c + 1.0#
            y = y + 1.0#
            z = z + 2.0#
            yc = y * c
            pk = pkm1 * z - pkm2 * yc
            qk = qkm1 * z - qkm2 * yc
            If qk <> 0.0# Then
                r = pk / qk
                t = Abs((ans - r) / r)
                ans = r
            Else
                t = 1.0#
            End If
            pkm2 = pkm1
            pkm1 = pk
            qkm2 = qkm1
            qkm1 = qk
            If Abs(pk) > IGammaBigNumber Then
                pkm2 = pkm2 * IGammaBigNumberInv
                pkm1 = pkm1 * IGammaBigNumberInv
                qkm2 = qkm2 * IGammaBigNumberInv
                qkm1 = qkm1 * IGammaBigNumberInv
            End If
        Loop Until t <= IGammaEpsilon
        result = ans * ax

        IncompleteGammaC = result
    End Function

    Public Function IncompleteGamma(ByVal a As Double, ByVal x As Double) As Double
        Dim result As Double
        Dim IGammaEpsilon As Double
        Dim ans As Double
        Dim ax As Double
        Dim c As Double
        Dim r As Double
        Dim Tmp As Double

        IGammaEpsilon = 0.000000000000001
        If x <= 0.0# Or a <= 0.0# Then
            result = 0.0#
            IncompleteGamma = result
            Exit Function
        End If
        If x > 1.0# And x > a Then
            result = 1.0# - IncompleteGammaC(a, x)
            IncompleteGamma = result
            Exit Function
        End If
        ax = a * Log(x) - x - LnGamma(a, Tmp)
        If ax < -709.782712893384 Then
            result = 0.0#
            IncompleteGamma = result
            Exit Function
        End If
        ax = Exp(ax)
        r = a
        c = 1.0#
        ans = 1.0#
        Do
            r = r + 1.0#
            c = c * x / r
            ans = ans + c
        Loop Until c / ans <= IGammaEpsilon
        result = ans * ax / a

        IncompleteGamma = result
    End Function

    Public Function LnGamma(ByVal x As Double, ByRef SgnGam As Double) As Double
        Dim result As Double
        Dim a As Double
        Dim B As Double
        Dim c As Double
        Dim P As Double
        Dim Q As Double
        Dim u As Double
        Dim w As Double
        Dim z As Double
        Dim i As Long
        Dim LogPi As Double
        Dim LS2PI As Double
        Dim Tmp As Double

        SgnGam = 1.0#
        LogPi = 1.1447298858494
        LS2PI = 0.918938533204673
        If x < -34.0# Then
            Q = -x
            w = LnGamma(Q, Tmp)
            P = Int(Q)
            i = Round(P)
            If i Mod 2.0# = 0.0# Then
                SgnGam = -1.0#
            Else
                SgnGam = 1.0#
            End If
            z = Q - P
            If z > 0.5 Then
                P = P + 1.0#
                z = P - Q
            End If
            z = Q * Sin(PI * z)
            result = LogPi - Log(z) - w
            LnGamma = result
            Exit Function
        End If
        If x < 13.0# Then
            z = 1.0#
            P = 0.0#
            u = x
            Do While u >= 3.0#
                P = P - 1.0#
                u = x + P
                z = z * u
            Loop
            Do While u < 2.0#
                z = z / u
                P = P + 1.0#
                u = x + P
            Loop
            If z < 0.0# Then
                SgnGam = -1.0#
                z = -z
            Else
                SgnGam = 1.0#
            End If
            If u = 2.0# Then
                result = Log(z)
                LnGamma = result
                Exit Function
            End If
            P = P - 2.0#
            x = x + P
            B = -1378.25152569121
            B = -38801.6315134638 + x * B
            B = -331612.992738871 + x * B
            B = -1162370.97492762 + x * B
            B = -1721737.0082084 + x * B
            B = -853555.664245765 + x * B
            c = 1.0#
            c = -351.815701436523 + x * c
            c = -17064.2106651881 + x * c
            c = -220528.590553854 + x * c
            c = -1139334.44367983 + x * c
            c = -2532523.07177583 + x * c
            c = -2018891.41433533 + x * c
            P = x * B / c
            result = Log(z) + P
            LnGamma = result
            Exit Function
        End If
        Q = (x - 0.5) * Log(x) - x + LS2PI
        If x > 100000000.0# Then
            result = Q
            LnGamma = result
            Exit Function
        End If
        P = 1.0# / (x * x)
        If x >= 1000.0# Then
            Q = Q + ((7.93650793650794 * 0.0001 * P - 2.77777777777778 * 0.001) * P + 0.0833333333333333) / x
        Else
            a = 8.11614167470508 * 0.0001
            a = -(5.95061904284301 * 0.0001) + P * a
            a = 7.93650340457717 * 0.0001 + P * a
            a = -(2.777777777301 * 0.001) + P * a
            a = 8.33333333333332 * 0.01 + P * a
            Q = Q + a / x
        End If
        result = Q

        LnGamma = result
    End Function

End Class