seed random number in VBA

[MetLife]

Hi,

I wanted to generate random numbers, but they need to be the same random numbers. So in C++ I recall you could seed the random number generator with an integer.

So Rnd(8) should generate the same sequence of numbers. How do we do this in Excel?

I notice that if I use Rnd(8) it generates the same ones but they are the same as Rnd(9) etc...

Sub test_array()
Dim x1(1 To 100, 1 To 200) As Double
Dim i As Integer, j As Integer

    For i = 1 To 100
        For j = 1 To 200
            x1(i, j) = Rnd(8)
            Range("G5").Offset(j, 0).Value = x1(i, j)
        Next j
    Next i

'1.) seed random number

End Sub

 

[Cubist]

In VBA, it's Randomize 8

See this link.

 

[MetLife]

using Randomize 8 doesn't work. The numbers always change.

Sub test_array()
Dim x1(1 To 200) As Double
Dim i As Integer, j As Integer

Randomize 8

    For i = 1 To 100
            x1(i) = Rnd()
            Range("G5").Offset(i, 0).Value = x1(i)
    Next i

MsgBox "done!"

End Sub

 

[thirty_two]

Use "Rnd (-1)" before the "Randomize" statement. That should generate the same sequence given a certain seed. This behavior is described in a Note in the "Randomize" documentation.

Ie:

Sub test_array()
Dim x1(1 To 200) As Double
Dim i As Integer, j As Integer

Rnd (-1)
Randomize 8

    For i = 1 To 100
            x1(i) = Rnd()
            Range("G5").Offset(i, 0).Value = x1(i)
    Next i

MsgBox "done!"

End Sub

 

[MetLife]

Thanks - I had read the documentation & it would have been helpful if they provided an example like you did.