数值分析报告 (李庆扬版)

《数值分析》作业

学院：机械学院

专业：机械工程

姓名：赵博

学号：2014520024

日期：2015年6月29日

第二章作业

问：用线性插值及二次插值计算ln0.54的近似值。

答：VB程序如下：

Option Explicit

Sub czfl(ByRef x() As Single, y() As Single, n As Integer, x1 As Double, f As Double) Dim i, j As Integer

Dim p As Single

Dim appexcel As Object

Dim wbmybook As Object

Dim wsmysheet As Object

Set appexcel = CreateObject("excel.application")

Set wbmybook = appexcel.workbooks.Add

Set wsmysheet = appexcel.worksheets.Add

f = 0

For i = 0 To n

p = 1

For j = 0 To n

If i <> j Then

p = p * (x1 - x(j)) / (x(i) - x(j))

End If

Next j

wsmysheet.cells(i + 1, 1) = Str(p)

wsmysheet.cells(i + 1, 2) = Str(p * y(i))

f = f + p * y(i)

Next i

wsmysheet.cells(n + 1, 3) = "最终结果" + Str(f)

appexcel.Visible = True

End Sub

Private Sub Command1_Click(Index As Integer)

Dim x() As Single

Dim y() As Single

Dim n As Integer

Dim k As Integer

Dim f As Double

k = 0

n = V al(Text1.Text)

ReDim x(n)

ReDim y(n)

Open "czfl.txt" For Output As #1

Print #1, Text3.Text

Close #1

Open "czfl.txt" For Input As #1

Do While Not EOF(1)

Input #1, x(k), y(k)

'Print x(k), y(k)

k = k + 1

Loop

Close #1

Select Case Index

Case 0

Call czfl(x(), y(), Text1.Text, Text2.Text, f)

Case 1

Call czfnt(x(), y(), Text1.Text, Text2.Text, f)

End Select

End Sub

Sub czfnt(ByRef x() As Single, y() As Single, n As Integer, x1 As Double, f As Double)

Dim i, j As Integer

Dim k, l As Integer

Dim s As Double

Dim appexcel As Object

Dim wbmybook As Object

Dim wsmysheet As Object

Set appexcel = CreateObject("excel.application")

Set wbmybook = appexcel.workbooks.Add

Set wsmysheet = appexcel.worksheets.Add

f = y(0)

s = 1

For j = 1 To n

For i = n To j Step -1

y(i) = (y(i) - y(i - 1)) / (x(i) - x(i - j))

wsmysheet.cells(i, j) = Str(y(i))

Next i

Next j

For k = 1 To n

s = s * (x1 - x(l))

f = f + s * y(k)

Next k

wsmysheet.cells(n, n + 1) = "最终结果" + Str(f)

appexcel.Visible = True

End Sub

结果：

1.线性插值

0.6 -0.41589

0.4 -0.20433 最终结果-.620218614056672 2.二次插值

-0.12 0.109955

0.84 -0.58224

0.28 -0.14303 最终结果-.615319814966043

第三章作业

求运动方程。

答：vb程序如下：（窗体见工程文件）Option Explicit

Option Base 1

Sub lufj(n As Integer, a() As Single, b() As Single) Dim i As Integer, j As Integer, k As Integer

Dim s As Single

For i = 2 To n

a(i, 1) = a(i, 1) / a(1, 1)

Next i

For i = 2 To n

For j = i To n

s = 0

For k = 1 To i - 1

s = s + a(i, k) * a(k, j)

Next k

a(i, j) = a(i, j) - s

Next j

For j = i + 1 To n

s = 0

For k = 1 To i - 1

s = s + a(j, k) * a(k, i)

Next k

a(j, i) = (a(j, i) - s) / a(i, i)

Next j

Next i

For i = 1 To n

s = 0

For j = 1 To i - 1

s = s + a(i, j) * b(j)

Next j

b(i) = b(i) - s

Next i

For i = n To 1 Step -1

s = 0

For j = i + 1 To n