betacf.txt

VB常用数值算法集 内含有解线性代数方程组

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