medfit.txt

数据拟合源程序

Public NDATAT, XT(1000), YT(1000), ARR(1000), AA, ABDEVT
Sub MEDFIT(X(), Y(), NDATA, A, B, ABDEV)
    SX = 0#
    SY = 0#
    SXY = 0#
    SXX = 0#
    For J = 1 To NDATA
        XT(J) = X(J)
        YT(J) = Y(J)
        SX = SX + X(J)
        SY = SY + Y(J)
        SXY = SXY + X(J) * Y(J)
        SXX = SXX + X(J) ^ 2
    Next J
    NDATAT = NDATA
    DEL = NDATA * SXX - SX ^ 2
    AA = (SXX * SY - SX * SXY) / DEL
    BB = (NDATA * SXY - SX * SY) / DEL
    CHISQ = 0#
    For J = 1 To NDATA
        CHISQ = CHISQ + (Y(J) - (AA + BB * X(J))) ^ 2
    Next J
    SIGB = Sqr(CHISQ / DEL)
    B1 = BB
    F1 = ROFUNC(B1)
    B2 = BB + Abs(3 * SIGB) * Sgn(F1)
    F2 = ROFUNC(B2)
1   If F1 * F2 > 0# Then
        BB = 2# * B2 - B1
        B1 = B2
        F1 = F2
        B2 = BB
        F2 = ROFUNC(B2)
        GoTo 1
    End If
    SIGB = 0.01 * SIGB
2   If Abs(B2 - B1) > SIGB Then
        BB = 0.5 * (B1 + B2)
        If BB = B1 Or BB = B2 Then GoTo 3
        F = ROFUNC(BB)
        If F * F1 >= 0# Then
            F1 = F
            B1 = BB
        Else
            F2 = F
            B2 = BB
        End If
        GoTo 2
    End If
3   A = AA
    B = BB
    ABDEV = ABDEVT / NDATA
End Sub