version VBA del codigo que publique antes en C
Const NMAX = 50
Sub main()
Dim s As Double
Dim i As Integer, npoints As Integer
Dim buffer(1 To NMAX, 1 To NMAX) As Double
s = 0
npoints = 13
buffer(1, 1) = 3: buffer(1, 2) = 3
buffer(2, 1) = 12: buffer(2, 2) = 3
buffer(3, 1) = 12: buffer(3, 2) = 6
buffer(4, 1) = 11: buffer(4, 2) = 6
buffer(5, 1) = 11: buffer(5, 2) = 7
buffer(6, 1) = 15: buffer(6, 2) = 7
buffer(7, 1) = 15: buffer(7, 2) = 9
buffer(8, 1) = 8: buffer(8, 2) = 9
buffer(9, 1) = 8: buffer(9, 2) = 6
buffer(10, 1) = 4: buffer(10, 2) = 6
buffer(11, 1) = 4: buffer(11, 2) = 9
buffer(12, 1) = 3: buffer(12, 2) = 9
buffer(13, 1) = 3: buffer(13, 2) = 3
For i = 1 To npoints - 1
s = s + (buffer(i, 1) + buffer(i + 1, 1)) * (buffer(i, 2) - buffer(i + 1, 2))
Next
s = Abs(s) / 2
MsgBox s
End Sub