# Tema18 - 18.14 Here is a VBA program to implement Newton...

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18.14 Here is a VBA program to implement Newton interpolation. It is set up to solve Example 18.5: Option Explicit Sub Newt() Dim n As Integer, i As Integer Dim yint(10) As Single, x(10) As Single, y(10) As Single Dim ea(10) As Single, xi As Single Range("a5").Select n = ActiveCell.Row Selection.End(xlDown).Select n = ActiveCell.Row - n Range("a5").Select For i = 0 To n x(i) = ActiveCell.Value ActiveCell.Offset(0, 1).Select y(i) = ActiveCell.Value ActiveCell.Offset(1, -1).Select Next i Range("e3").Select xi = ActiveCell.Value
Call Newtint(x(), y(), n, xi, yint, ea) Sheets("Sheet1").Select Range("d5:f25").ClearContents Range("d5").Select For i = 0 To n ActiveCell.Value = i ActiveCell.Offset(0, 1).Select ActiveCell.Value = yint(i) ActiveCell.Offset(0, 1).Select ActiveCell.Value = ea(i) ActiveCell.Offset(1, -2).Select Next i Range("a5").Select End Sub Sub Newtint(x, y, n, xi, yint, ea) Dim i As Integer, j As Integer, order As Integer Dim fdd(10, 10) As Single, xterm As Single Dim yint2 As Single For i = 0 To n fdd(i, 0) = y(i) Next i For j = 1 To n For i = 0 To n - j fdd(i, j) = (fdd(i + 1, j - 1) - fdd(i, j - 1)) / (x(i + j) - x(i)) Next i Next j xterm = 1# yint(0) = fdd(0, 0) For order = 1 To n xterm = xterm * (xi - x(order - 1)) yint2 = yint(order - 1) + fdd(0, order) * xterm ea(order - 1) = yint2 - yint(order - 1) yint(order) = yint2 Next order End Sub 18.15 Here is the solution when the program from Prob. 18.14 is run. 18.16 See solutions for Probs. 18.1 through 18.3. 18.17 A plot of the error can easily be added to the Excel application. The following shows the solution for Prob. 18.4:

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The following shows the solution for Prob. 18.5: 18.18
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Tema18 - 18.14 Here is a VBA program to implement Newton...

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