splint.txt

用VB实现多种数值插值方法。包括：接格朗日

Sub SPLINT(XA(), YA(), Y2A(), N, X, Y)
    KLO = 1
    KHI = N
1   If KHI - KLO > 1 Then
        K = (KHI + KLO) / 2
        If XA(K) > X Then
            KHI = K
        Else
            KLO = K
        End If
        GoTo 1
    End If
    H = XA(KHI) - XA(KLO)
    If H = 0 Then
        Print "  PAUSE  'BAD  XA  INPUT'"
        Exit Sub
    End If
    A = (XA(KHI) - X) / H
    B = (X - XA(KLO)) / H
    AAA = A * YA(KLO) + B * YA(KHI)
    BBB = (A ^ 3 - A) * Y2A(KLO) + (B ^ 3 - B) * Y2A(KHI)
    Y = AAA + BBB * (H ^ 2) / 6#
End Sub