
Oct 11th, 2007, 04:01 AM
#1
Thread Starter
New Member
Gauss Elimination in Visual Basic
Well, I have some code here. My professor wants us to write this same program in Excel (same result) but do so without the "b" variable. Not sure 100% where to begin.
Code:
Option Explicit
Private a(20, 20) As Double, b(20) As Double
Private i As Integer, j As Integer, n As Integer
Private k As Integer
Private factor As Double
Private x(20) As Double, sum As Double
Sub gaussturkoglu()
n = 3 'number of equations
'Reading A and b
For i = 1 To n
For j = 1 To n
a(i, j) = Cells(i, j)
Next j
b(i) = Cells(i, n + 1)
Next i
'Forward Elimination
For k = 1 To n  1
For i = k + 1 To n Step 1
factor = a(i, k) / a(k, k)
For j = k + 1 To n
a(i, j) = a(i, j)  factor * a(k, j)
Next j
b(i) = b(i)  factor * b(k)
Next i
Next k
'Outputing A and b after forward elimination
For i = 1 To n
For j = 1 To n
Cells(n + 1 + i, j).Value = a(i, j)
Next j
Cells(n + 1 + i, n + 1) = b(i)
Next i
'Back Substitution
x(n) = b(n) / a(n, n)
For i = n  1 To 1 Step 1
sum = 0
For j = n To i + 1 Step 1 'or j=i+1 to n
sum = sum + a(i, j) * x(j)
Next j
x(i) = (b(i)  sum) / a(i, j)
Next i
'Output x
For i = 1 To n
Cells(i, n + 3) = x(i)
Next i
End Sub
Last edited by Hack; Oct 11th, 2007 at 06:33 AM.
Reason: Added Code Tags

Oct 11th, 2007, 06:34 AM
#2
Re: Gauss Elimination in Visual Basic
Moved to Office Development

Oct 16th, 2007, 12:32 PM
#3
Fanatic Member
Re: Gauss Elimination in Visual Basic
Perhaps your professor means using the augmented matrix technique?
http://www.math.csusb.edu/math110/sr...s/solsys.html

Jul 22nd, 2011, 04:08 PM
#4
New Member
Re: Gauss Elimination in Visual Basic
Originally Posted by hed0nisticpat
Well, I have some code here. My professor wants us to write this same program in Excel (same result) but do so without the "b" variable. Not sure 100% where to begin.
Code:
Option Explicit
Private a(20, 20) As Double, b(20) As Double
Private i As Integer, j As Integer, n As Integer
Private k As Integer
Private factor As Double
Private x(20) As Double, sum As Double
Sub gaussturkoglu()
n = 3 'number of equations
'Reading A and b
For i = 1 To n
For j = 1 To n
a(i, j) = Cells(i, j)
Next j
b(i) = Cells(i, n + 1)
Next i
'Forward Elimination
For k = 1 To n  1
For i = k + 1 To n Step 1
factor = a(i, k) / a(k, k)
For j = k + 1 To n
a(i, j) = a(i, j)  factor * a(k, j)
Next j
b(i) = b(i)  factor * b(k)
Next i
Next k
'Outputing A and b after forward elimination
For i = 1 To n
For j = 1 To n
Cells(n + 1 + i, j).Value = a(i, j)
Next j
Cells(n + 1 + i, n + 1) = b(i)
Next i
'Back Substitution
x(n) = b(n) / a(n, n)
For i = n  1 To 1 Step 1
sum = 0
For j = n To i + 1 Step 1 'or j=i+1 to n
sum = sum + a(i, j) * x(j)
Next j
x(i) = (b(i)  sum) / a(i, j)
Next i
'Output x
For i = 1 To n
Cells(i, n + 3) = x(i)
Next i
End Sub
I applied your code and it seemed it helped me. But what I cant understand clearly is why is it important to read the matrix and the vector (refering to the portion "'Reading A and b"). How does it work?
Thank you.

Jul 22nd, 2011, 04:08 PM
#5
New Member
Re: Gauss Elimination in Visual Basic
I applied your code and it seemed it helped me. But what I cant understand clearly is why is it important to read the matrix and the vector (refering to the portion "'Reading A and b"). How does it work?
Thank you.
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