Gaussian elimination: Difference between revisions

=={{header|VBA}}==

{{trans|Phix}}<lang vb>'Option Base 1

Private Function gauss_eliminate(a As Variant, b As Variant) As Variant

Dim n As Integer: n = UBound(b)

Dim tmp As Variant, m As Integer, mx As Variant

For col = 1 To n

m = col

mx = a(m, m)

For i = col + 1 To n

tmp = Abs(a(i, col))

If tmp > mx Then

m = i

mx = tmp

End If

Next i

If col <> m Then

For j = 1 To UBound(a, 2)

tmp = a(col, j)

a(col, j) = a(m, j)

a(m, j) = tmp

Next j

tmp = b(col)

b(col) = b(m)

b(m) = tmp

End If

For i = col + 1 To n

tmp = a(i, col) / a(col, col)

For j = col + 1 To n

a(i, j) = a(i, j) - tmp * a(col, j)

Next j

a(i, col) = 0

b(i) = b(i) - tmp * b(col)

Next i

Next col

Dim x() As Variant

ReDim x(n)

For col = n To 1 Step -1

tmp = b(col)

For j = n To col + 1 Step -1

tmp = tmp - x(j) * a(col, j)

Next j

x(col) = tmp / a(col, col)

Next col

gauss_eliminate = x

End Function

Public Sub main()

a = [{1.00, 0.00, 0.00, 0.00, 0.00, 0.00; 1.00, 0.63, 0.39, 0.25, 0.16, 0.10; 1.00, 1.26, 1.58, 1.98, 2.49, 3.13; 1.00, 1.88, 3.55, 6.70, 12.62, 23.80; 1.00, 2.51, 6.32, 15.88, 39.90, 100.28; 1.00, 3.14, 9.87, 31.01, 97.41, 306.02}]

b = [{-0.01, 0.61, 0.91, 0.99, 0.60, 0.02}]

Dim s() As String, x() As Variant

ReDim s(UBound(b)), x(UBound(b))

Debug.Print "(";

x = gauss_eliminate(a, b)

For i = 1 To UBound(x)

s(i) = CStr(x(i))

Next i

t = Join(s, ", ")

Debug.Print t; ")"

End Sub</lang>{{out}}

<pre>(-0.01, 1.60279039450209, -1.61320305990548, 1.24549412137136, -0.490989719584628, 0.065760696175228)</pre>