by Angsuman Banerji (23 Submissions)
Category: Math/Dates
Compatability: VB.NET
Difficulty: Unknown Difficulty
Originally Published: Fri 4th January 2008
Date Added: Mon 8th February 2021
Rating: 
(1 Votes)
Perform Gaussian Elimination method to solve a system of n-variables of n-linear system of equations.
API Declarations
Private mat() As Single, NoOfVariableEquations As Integer
VBcoders
Dim mBound As Integer, i As Integer, j As Integer
NoOfVariableEquations = Val(InputBox("Number of variables", "Equations", 3))
If NoOfVariableEquations <= 0 Then Exit Sub ' nothing2do
mBound = NoOfVariableEquations - 1
If mBound > 1 Then ReDim mat(mBound, mBound + 1)
For i = 0 To mBound
For j = 0 To mBound
mat(i, j) = InputBox("Enter Element co-eff value" & vbNewLine & _
"Element [" & i & "," & j & "]", "Input Data Element")
Next j
mat(i, mBound + 1) = InputBox("Enter Element Value" & vbNewLine & _
"Value [" & i & "," & mBound + 1 & "]", "Input Equation Value")
Next i
Print "Matrix representation of the linear Equations"
Call DisplayMatrixData
Call UpperTriangular
Print "converted to Upper Triangular form"
Call DisplayMatrixData
Call BkSubst
End Sub
Private Sub DisplayMatrixData()
Dim i As Integer, j As Integer, res As String
For i = 0 To NoOfVariableEquations - 1
For j = 0 To NoOfVariableEquations
res = res & vbTab & mat(i, j)
Next j
res = res & vbNewLine
Next i
MsgBox res: Print res & vbNewLine
End Sub
Private Sub UpperTriangular() ' Matrix to Echelon form
Dim i As Integer, j As Integer, k As Integer, mBound As Integer
Dim df As Single
mBound = NoOfVariableEquations - 1
For k = 0 To mBound - 1
For i = k + 1 To mBound
If Abs(mat(k, k)) < Abs(mat(i, k)) Then Call swapRowMat(i, k)
df = mat(i, k) / mat(k, k)
For j = k To 3
mat(i, j) = FormatNumber(mat(i, j) - mat(k, j) * df, 4)
Next j
Next i
Next k
End Sub
Private Sub swapRowMat(ByVal r1 As Integer, ByVal r2 As Integer)
Dim i As Integer, mB As Integer, dVal As Single
mB = NoOfVariableEquations
For i = 0 To mB
dVal = mat(r1, i): mat(r1, i) = mat(r2, i): mat(r2, i) = dVal
Next i
End Sub
Private Sub BkSubst() ' BackSubstitution
Dim i As Integer, j As Integer, mBound As Integer, sSum As Single
mBound = NoOfVariableEquations - 1
ReDim reslt(mBound) As Single
reslt(mBound) = mat(mBound, mBound + 1) / mat(mBound, mBound)
For i = mBound - 1 To 0 Step -1
sSum = 0
For j = i + 1 To mBound
sSum = sSum + mat(i, j) * reslt(j)
Next j
reslt(i) = FormatNumber((mat(i, mBound + 1) - sSum) / mat(i, i), 5)
Next i
Dim msgStr As String
For i = 0 To mBound
msgStr = msgStr + vbNewLine & "X" & i + 1 & vbTab & reslt(i)
Next i
MsgBox msgStr, , "Result"
Print "Solution of Equations" & msgStr
End Sub
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