ratint.txt

VB常用数值算法集 内含有解线性代数方程组

Sub RATINT(XA(), YA(), N, X, Y, DY)
    TINY = 1E-25
    Dim C(10), D(10)
    NS = 1
    HH = Abs(X - XA(1))
    For I = 1 To N
        H = Abs(X - XA(I))
        If H = 0 Then
            Y = YA(I)
            DY = 0#
            Exit Sub
        ElseIf H < HH Then
            NS = I
            HH = H
        End If
        C(I) = YA(I)
        D(I) = YA(I) + TINY
    Next I
    Y = YA(NS)
    NS = NS - 1
    For M = 1 To N - 1
        For I = 1 To N - M
            W = C(I + 1) - D(I)
            H = XA(I + M) - X
            T = (XA(I) - X) * D(I) / H
            DD = T - C(I + 1)
            If DD = 0# Then
                Print "PAUSE"
                Exit Sub
            End If
            DD = W / DD
            D(I) = C(I + 1) * DD
            C(I) = T * DD
        Next I
        If 2 * NS < N - M Then
            DY = C(NS + 1)
        Else
            DY = D(NS)
            NS = NS - 1
        End If
        Y = Y + DY
    Next M
End Sub