VERSION 5.00
Begin VB.Form Form1 
   Caption         =   "Form1"
   ClientHeight    =   5985
   ClientLeft      =   2265
   ClientTop       =   750
   ClientWidth     =   5115
   LinkTopic       =   "Form1"
   ScaleHeight     =   5985
   ScaleWidth      =   5115
   Begin VB.CommandButton Command1 
      Caption         =   "Command1"
      Height          =   375
      Left            =   3240
      TabIndex        =   0
      Top             =   5160
      Width           =   1335
   End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Private Sub Command1_ClicK()
    'PROGRAM D4R13
    'Driver for routine BETAI BETACF
    Open "D:\VB常用數值算法集\DATA\FNCVAL.DAT" For Input As #1
    Do
      Line Input #1, Text$
    Loop While Text$ <> "Incomplete Beta Function"
    Line Input #1, NVAL$
    NVAL = Val(NVAL$)
    Print Text$
    Print
    Print "     A        B           X       Actual    BETAI(X)"
    For I = 1 To NVAL
        Line Input #1, DUM$
        A = Val(Mid(DUM$, 1, 7))
        B = Val(Mid(DUM$, 8, 7))
        X = Val(Mid(DUM$, 15, 7))
        Value = Val(Mid(DUM$, 22))
        Print Tab(4); Format$(A, "#0.00");
        Print Tab(11); Format$(B, "#0.####00");
        Print Tab(23); Format$(X, "0.000000");
        Print Tab(34); Format$(Value, "0.000000");
        Print Tab(45); Format$(BETAI(A, B, X), "0.000000");
    Next I
    Close #1
End Sub
Function BETACF(A, B, X)
    ITMAX = 100
    EPS = 0.0000003
    AM = 1#
    BM = 1#
    AZ = 1#
    QAB = A + B
    QAP = A + 1#
    QAM = A - 1#
    BZ = 1# - QAB * X / QAP
    For M = 1 To ITMAX
        EM = M
        TEM = EM + EM
        D = EM * (B - M) * X / ((QAM + TEM) * (A + TEM))
        AP = AZ + D * AM
        BP = BZ + D * BM
        D = -(A + EM) * (QAB + EM) * X / ((A + TEM) * (QAP + TEM))
        AAP = AP + D * AZ
        BPP = BP + D * BZ
        AOLD = AZ
        AM = AP / BPP
        BM = BP / BPP
        AZ = AAP / BPP
        BZ = 1#
        If Abs(AZ - AOLD) < EPS * Abs(AZ) Then GoTo 1
    Next M
    Print "A or B too big, or ITMAX too small"
1   BETACF = AZ
End Function
Function BETAI(A, B, X)
    If X < 0# Or X > 1# Then Print "bad argument X in BETAI"
    If X = 0# Or X = 1# Then
        BT = 0#
    Else
        AAA = GAMMLN(A + B) - GAMMLN(A) - GAMMLN(B)
        BT = Exp(AAA + A * Log(X) + B * Log(1# - X))
    End If
    If X < (A + 1#) / (A + B + 2#) Then
        BETAI = BT * BETACF(A, B, X) / A
        Exit Function
    Else
        BETAI = 1# - BT * BETACF(B, A, 1# - X) / B
        Exit Function
    End If
End Function
   Function GAMMLN(XX)
      Dim COF(6)
      COF(1) = 76.18009173
      COF(2) = -86.50532033
      COF(3) = 24.01409822
      COF(4) = -1.231739516
      COF(5) = 0.00120858003
      COF(6) = -0.00000536382
      STP = 2.50662827465
      HALF = 0.5
      ONE = 1#
      FPF = 5.5
      X = XX - ONE
      TMP = X + FPF
      TMP = (X + HALF) * Log(TMP) - TMP
      SER = ONE
      For J = 1 To 6
          X = X + ONE
          SER = SER + COF(J) / X
    Next J
      GAMMLN = TMP + Log(STP * SER)
   End Function