polint.txt

用VB实现多种数值插值方法。包括：接格朗日

Sub POLINT(XA(), YA(), N, X, Y, DY)
    Dim C(10), D(10)
    NS = 1
    DIF = Abs(X - XA(1))
    For I = 1 To N
        DIFT = Abs(X - XA(I))
        If DIFT < DIF Then
            NS = I
            DIF = DIFT
        End If
        C(I) = YA(I)
        D(I) = YA(I)
    Next I
    Y = YA(NS)
    NS = NS - 1
    For M = 1 To N - 1
        For I = 1 To N - M
            HO = XA(I) - X
            HP = XA(I + M) - X
            W = C(I + 1) - D(I)
            DEN = HO - HP
            If DEN = 0# Then
                Print "PAUSE"
                Exit Sub
            End If
            DEN = W / DEN
            D(I) = HP * DEN
            C(I) = HO * DEN
        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