d14r2.txt

VB常用数值算法集 内含有解线性代数方程组

Private Sub Command1_Click()
    'PROGRAM D14R2
    'Driver for routine RKDUMB
    NVAR = 4
    NSTEP = 150
    Dim VSTART(4), XX(200), Y(10, 200)
    X1 = 1#
    VSTART(1) = BESSJ0(X1)
    VSTART(2) = BESSJ1(X1)
    VSTART(3) = BESSJ(2, X1)
    VSTART(4) = BESSJ(3, X1)
    X2 = 20#
    Call RKDUMB(VSTART(), NVAR, X1, X2, NSTEP, XX(), Y())
    Print
    Print Tab(5); "  X        Integrated     BESSJ3"
    For I = 1 To CInt(NSTEP / 10)
        J = 10 * I
        Print Tab(5); Format$(XX(J), "##.###0");
        Print Tab(17); Format$(Y(4, J), ".#####0");
        Print Tab(30); Format$(BESSJ(3, XX(J)), ".#####0")
    Next I
End Sub
Sub DERIVS(X, Y1(), DYDX())
    DYDX(1) = -Y1(2)
    DYDX(2) = Y1(1) - (1# / X) * Y1(2)
    DYDX(3) = Y1(2) - (2# / X) * Y1(3)
    DYDX(4) = Y1(3) - (3# / X) * Y1(4)
End Sub