Matrix Inverse message box help

A

Arcadian Myth

New Member
Joined
Apr 1, 2022
Messages
2
Office Version
  1. 365
Platform
  1. Windows
Hello all,

I'm new to this forum, but I feel like this is a great place to get help. I am trying to find the correct If Then coding to use that will pop up a message box if there is no inverse to a matrix, but everything I have tried has failed. The closest I have gotten to something that works is the following:

If Solution = True Then
Selection.Copy
Sheets("Solution").Select
Sheets("Solution").Range("B5").Resize(rowsize:=nRowA, columnsize:=nColA).Select
Selection.FormulaArray = "=MINVERSE(Amat)"
Selection.Font.Bold = True
Application.CutCopyMode = False
Else
strMessage = "Matrix does not have an Inverse"
MsgBox strMessage
Sheets("Solution").Select
Selection.ClearContents
End If

But this prompts the message box whether there is an answer or not. I spent a few hours on google trying to find a solution, and that's how I got here. Please help me understand how to do this. I was thinking using the fact that an inverse that does not exist gives a calculation error of #NUM! and somehow integrating that into the If Then statement, but I don't know the commands, or how to even start that. Please help.
 

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A previous post in this forum had this suggestion. I have not tested it. on very large matrices

Code: 
Sub GaussJordan()

    Dim a As Variant, c#(), x#, y#
    Dim m&, u#, i&, j&, rv&()
    Dim q&, w&


    Set a = Cells(1).CurrentRegion
    m = a.Rows.Count 'UBound(a, 1)
    ReDim c(1 To m, 1 To m), rv(1 To m, 1 To 2)
    For i = 1 To m: c(i, i) = 1: Next i
        For q = 1 To m
            u = 10 ^ 15
            For i = 1 To m
                If rv(i, 1) = 0 Then
                    If a(i, q) <> 0 Then
                        If (Log(a(i, q) ^ 2)) ^ 2 < u Then
                            u = (Log(a(i, q) ^ 2)) ^ 2
                            w = i
                        End If
                    End If
                End If
            Next i


            rv(w, 1) = w: rv(q, 2) = w: x = a(w, q)
            For j = 1 To m
                a(w, j) = a(w, j) / x
                c(w, j) = c(w, j) / x
            Next j
            For i = 1 To m
                If rv(i, 1) = 0 Then
                    y = a(i, q)
                    For j = 1 To m
                        a(i, j) = a(i, j) - y * a(w, j)
                        c(i, j) = c(i, j) - y * c(w, j)
                    Next j
                End If
            Next i, q
            
 'BACK SOLUTION
            For q = m To 2 Step -1: For w = q - 1 To 1 Step -1
                x = a(rv(w, 2), q)
                a(rv(w, 2), q) = a(rv(w, 2), q) - x * a(rv(q, 2), q)
                For j = 1 To m
                    c(rv(w, 2), j) = c(rv(w, 2), j) - x * c(rv(q, 2), j)
                Next j
            Next w, q
            For q = 1 To m: For j = 1 To m
                a(q, j) = c(rv(q, 2), j)
            Next j, q
            Cells(m + 2, 1).Resize(m, m) = a


        End Sub
 
Upvote 0
BTW: you an use MDETERM(array) to find out if there is a non-zero determinant or, if 0, there is no inverse.
Place that in the beginning of your code and handle accordingly.
 
Upvote 0
kweaver said:
A previous post in this forum had this suggestion. I have not tested it. on very large matrices

Code: 
Sub GaussJordan()

    Dim a As Variant, c#(), x#, y#
    Dim m&, u#, i&, j&, rv&()
    Dim q&, w&


    Set a = Cells(1).CurrentRegion
    m = a.Rows.Count 'UBound(a, 1)
    ReDim c(1 To m, 1 To m), rv(1 To m, 1 To 2)
    For i = 1 To m: c(i, i) = 1: Next i
        For q = 1 To m
            u = 10 ^ 15
            For i = 1 To m
                If rv(i, 1) = 0 Then
                    If a(i, q) <> 0 Then
                        If (Log(a(i, q) ^ 2)) ^ 2 < u Then
                            u = (Log(a(i, q) ^ 2)) ^ 2
                            w = i
                        End If
                    End If
                End If
            Next i


            rv(w, 1) = w: rv(q, 2) = w: x = a(w, q)
            For j = 1 To m
                a(w, j) = a(w, j) / x
                c(w, j) = c(w, j) / x
            Next j
            For i = 1 To m
                If rv(i, 1) = 0 Then
                    y = a(i, q)
                    For j = 1 To m
                        a(i, j) = a(i, j) - y * a(w, j)
                        c(i, j) = c(i, j) - y * c(w, j)
                    Next j
                End If
            Next i, q
           
 'BACK SOLUTION
            For q = m To 2 Step -1: For w = q - 1 To 1 Step -1
                x = a(rv(w, 2), q)
                a(rv(w, 2), q) = a(rv(w, 2), q) - x * a(rv(q, 2), q)
                For j = 1 To m
                    c(rv(w, 2), j) = c(rv(w, 2), j) - x * c(rv(q, 2), j)
                Next j
            Next w, q
            For q = 1 To m: For j = 1 To m
                a(q, j) = c(rv(q, 2), j)
            Next j, q
            Cells(m + 2, 1).Resize(m, m) = a


        End Sub
Click to expand...
I'm trying to build off the code I was given. The red text is the code that does not work. This is the code I'm using for the inverse matirx:

Sub A_Inverse()
'
' A_Inverse Macro
'
Sheets("Solution").Select
Sheets("Solution").Range("B5").Select
Selection.CurrentRegion.Select
Selection.ClearContents
Sheets("Matrix A").Select
Sheets("Matrix A").Range("B5").Select
Selection.CurrentRegion.Select
Selection.Name = "Amat"
nRowA = Sheets("Matrix A").Range("Amat").Rows.Count
nColA = Sheets("Matrix A").Range("Amat").Columns.Count
If Solution = True Then
Selection.Copy
Sheets("Solution").Select
Sheets("Solution").Range("B5").Resize(rowsize:=nRowA, columnsize:=nColA).Select
Selection.FormulaArray = "=MINVERSE(Amat)"
Selection.Font.Bold = True
Application.CutCopyMode = False
Else
strMessage = "Matrix does not have an Inverse"
MsgBox strMessage
Sheets("Solution").Select
Selection.ClearContents
End If

'
End Sub

And I'm trying to keep it clean looking:

1649040415339.png
 
Upvote 0
With the matrix initiating in A1, try this:

Code: 
Sub GaussJordan()

    Dim a As Variant, c#(), x#, y#
    Dim m&, u#, i&, j&, rv&()
    Dim q&, w&


    Set a = Cells(1).CurrentRegion
    
[COLOR=rgb(184, 49, 47)]    If 0 = Application.WorksheetFunction.MDeterm(Cells(1).CurrentRegion) Then
     MsgBox "No Inverse"
     Exit Sub
     Else
    End If[/COLOR]
    
    m = a.Rows.Count 'UBound(a, 1)
    ReDim c(1 To m, 1 To m), rv(1 To m, 1 To 2)
    For i = 1 To m: c(i, i) = 1: Next i
        For q = 1 To m
            u = 10 ^ 15
            For i = 1 To m
                If rv(i, 1) = 0 Then
                    If a(i, q) <> 0 Then
                        If (Log(a(i, q) ^ 2)) ^ 2 < u Then
                            u = (Log(a(i, q) ^ 2)) ^ 2
                            w = i
                        End If
                    End If
                End If
            Next i


            rv(w, 1) = w: rv(q, 2) = w: x = a(w, q)
            For j = 1 To m
                a(w, j) = a(w, j) / x
                c(w, j) = c(w, j) / x
            Next j
            For i = 1 To m
                If rv(i, 1) = 0 Then
                    y = a(i, q)
                    For j = 1 To m
                        a(i, j) = a(i, j) - y * a(w, j)
                        c(i, j) = c(i, j) - y * c(w, j)
                    Next j
                End If
            Next i, q
            
 'BACK SOLUTION
            For q = m To 2 Step -1: For w = q - 1 To 1 Step -1
                x = a(rv(w, 2), q)
                a(rv(w, 2), q) = a(rv(w, 2), q) - x * a(rv(q, 2), q)
                For j = 1 To m
                    c(rv(w, 2), j) = c(rv(w, 2), j) - x * c(rv(q, 2), j)
                Next j
            Next w, q
            For q = 1 To m: For j = 1 To m
                a(q, j) = c(rv(q, 2), j)
            Next j, q
            Cells(m + 2, 1).Resize(m, m) = a


        End Sub [code]
 
Upvote 0
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