插值法VB源程序

1、第四章插值方法VB一、线性插值应用实例VB1已知：169的平方根为13,196的平方根为14，编程求175的平方根。Private Sub Comma nd1_click()Dim x(1 To 2),y(1 To 2) As Si nglex(1)=169:y=13x(2)=196:y(2)=14x0=175yO=F(x,y,xO)a=Format$(yO,#.#)Text1.Text=yO= & Str$(a)End SubPrivate Fun cti on F(x,y,xO)F=y(1)+(y (2)-y(1)/(x (2)-x(1)*(x0-x(1)End Fun cti on线性插

2、值应用实例VB2已知水的温度与密度和关系如下:温度5.010.015.020.025.030.0密度0.99990.9970.990.990.990.99试编程计算温度为 6、13、16、19、23、26 oC时的密度。Private Sub Comma nd1_click()N = 6X = Array(0, 5, 10, 15, 20, 25, 30)Y = Array(0, 0.999965, 0.9997, 0.999099, 0.998203, 0.997044, 0.995646)xc = Array(0, 6, 13, 16, 19, 23, 26)List1.Addltem x

3、0 & y0For I = 1 To 6X0 = xc(I)Y0 = f(N, X, Y , X0)List1.AddItem Str$(X0) & Str$(Y0)Next IEnd SubPrivate Function f(N, X, Y , X0)For I = 1 To NIf X0 = X(I) The nW = IExit ForEnd IfNext IW = W - 1If W = N ThenW = N - 1: End Iff = Y(W) + (Y(W + 1) - Y(W) / (X(W + 1) - X(W) * (XO - X(W)End Fun cti on二、拉

4、格朗日三点插值实例例：实验测得25OC乙醇溶液的平均摩尔体积v与乙醇的摩尔分数xi的关系数据如下表。试编程求摩尔数xi为0.3时的乙醇溶液的平均体积v。VB清单Dim X, v计 Wv21.2222.1623.1824.3225.5726.95xi0.0890.1150.1430.1730.2060.242v28.4730.1532.0134.0736.37xi0.2810.3230.3690.4200.477找牯巾|日二点Jit.怛Private Sub Command1_click()N = 11X = Array(0, 0.0891, 0.1153, 0.1435, 0.1739, 0.

5、2068, 0.2424, 0.2811, 0.3234, 0.3697, 0.4207, 0.4771)v = Array(0, 21.22, 22.16, 23.18, 24.32, 25.57, 26.95, 28.47, 30.15, 32.01, 34.07, 36.37)M = 3X0 = Val(Text1.Text)If X0 X(N) ThenPrint errorElseEnd If Call pt(N, M, X0, A, B) v0 = F(X0, A, B) List1.AddItem a= & A List1.AddItem b= & B List1.AddItem

6、 X0= & X0List1.AddItem v0= & Format$(v0, #.#) End SubPrivate Sub pt(N, M, X0, A, B) For I = 1 To NIf X0 = X(I) ThenIf Abs(X0 - X(I - 1) = Abs(X0 - X(I) Then A = I - Int(M + 1) / 2)Exit ForEnd IfElseA = I - Int(M / 2)End If Next IIf A = N ThenB = N: End IfA = B - M + 1End SubPrivate Function F(X0, A,

7、 B) For I = A To BW = 1For J = A To B If J I ThenW = W * (X0 - X(J) / (X(I) - X(J): End If Next J s = s + W * v(I)Next I F = s End Function三、拉格朗日全点插值 VB试对上例编程对比利用三个、五个、七个、九个和全部节点时，摩尔分数 xi 为 0.30 时乙醇溶液的平均摩尔体积 v。Dim X, vPrivate Sub Command1_click()N = 11X = Array(0, 0.0891, 0.1153, 0.1435, 0.1739, 0.2

8、068, 0.2424, 0.2811, 0.3234, 0.3697, 0.4207, 0.4771)v = Array(0, 21.22, 22.16, 23.18, 24.32, 25.57, 26.95, 28.47, 30.15, 32.01, 34.07, 36.37)X0 = Val(Text1.Text)If X0 X(N) ThenPrint errorEndElseEnd IfList1.AddItem x0= & X0For M = 3 To N Step 2Call pt(N, M, X0, A, B) v0 = F(X0, A, B)List1.AddItem M= & M & A= & A & B= & B & v0 & Format$(v0, #.#)Next MEnd SubPrivate Sub pt(N, M, X0, A, B)For I = 1 To NIf X0 = X(I) ThenIf Abs(X0 - X(I - 1) = Abs(X0 - X(I) ThenA = I - Int(M + 1) / 2)Exit ForEnd IfElseA = I - Int(M / 2)End IfNext IIf A = N ThenB = N: End IfA = B - M + 1End SubPrivate Function F(X0