Sub gauss_jordan()
Dim a As Variant, c#(), x#, y#
Dim m&, u#, i&, j&, rv&()
Dim q&, w&, mnx#
a = Cells(1).CurrentRegion
m = 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: mnx = u
For i = 1 To m
If rv(i, 1) = 0 Then
If Not 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)
If Abs(x) < mnx Then mnx = Abs(x)
If mnx < 10 ^ (-5) Then MsgBox "matrix may be singular": Exit Sub
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 + 4, 1).Resize(m, m) = a
'Cells(m + 2, 1) = mnx
End Sub
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