"AW" wrote in message news:h6jt3558jmhnt7av632plpl7ljisto48q5@4ax.com...
> Simple(?) program to draw random lines in a rectangle but when I
> discard all random lines longer than size and graph the results I get
> a set of diagonal bands. How can random lines have a pattern? Can
> anyone explain? When I discard a line, I generate a new random line
> until is it short enough - so how can it not be random?
> Win XP & VB 2008 Express. Thanks.
> --------------------------
> Imports System
> Imports System.Drawing
> Imports Microsoft.VisualBasic
> Imports Microsoft.VisualBasic.VBMath
> Imports Microsoft.VisualBasic.PowerPacks
> Public Class Form1
>    Dim rec As New RectangleShape
>    Dim arx(5000, 2) As Integer
>    Dim ary(5000, 2) As Integer
>    Public Sub New()
>        InitializeComponent()
>        Randomize()
>        Me.rec.Left = 300
>        Me.rec.Top = 2
>        Me.rec.Width = 900
>        Me.rec.Height = 900
>        For n = 0 To 4999
>            arx(n, 0) = arx(n, 1) = ary(n, 0) = ary(n, 1) = 0
>        Next
>    End Sub
>    Private Sub Form1_Paint(ByVal sender As Object, ByVal e As
> System.Windows.Forms.PaintEventArgs) Handles Me.Paint
>        PGr()
>    End Sub
>    Private Sub PGr()
>        Dim e As Graphics
>        e = Me.CreateGraphics
>        e.FillRectangle(Brushes.White, rec.Left, rec.Top, rec.Width,
> rec.Height)
>        For n = 0 To 4999
>            e.DrawLine(Pens.Black, rec.Left + arx(n, 0), rec.Top +
> ary(n, 0), _
>                       rec.Left + arx(n, 1), rec.Top + ary(n, 1))
>        Next
>    End Sub
>    Private Sub ReP_Click(ByVal sender As Object, ByVal e As
> System.EventArgs) Handles ReP.Click
>        Dim Dret As Integer = 0
>        For n = 0 To 4999
>            Do
>                arx(n, 0) = Int(Rnd() * 900)
>                arx(n, 1) = Int(Rnd() * 900)
>                ary(n, 0) = Int(Rnd() * 900)
>                ary(n, 1) = Int(Rnd() * 900)
>                Dret = Dist(n)
>            Loop Until Dret = 1
>        Next
>        PGr()
>    End Sub
>    Private Function Dist(ByVal n As Integer) As Integer
>        Dim x1, x2, y1, y2, h, h1, h2, size As Double
>        size = 40
>        x1 = arx(n, 0)
>        x2 = arx(n, 1)
>        h1 = Math.Pow((x1 - x2), 2)
>        y1 = ary(n, 0)
>        y2 = ary(n, 1)
>        h2 = Math.Pow((y1 - y2), 2)
>        h = h1 + h2
>        h = Math.Sqrt(h)
>        If h > size Then Return 0
>        Return 1
>    End Function
>    Private Sub Quit_Click(ByVal sender As Object, ByVal e As
> System.EventArgs) Handles Quit.Click
>        End
>    End Sub
> End Class
>

>"AW" wrote in message news:h6jt3558jmhnt7av632plpl7ljisto48q5@4ax.com...
>> Simple(?) program to draw random lines in a rectangle but when I
>> discard all random lines longer than size and graph the results I get
>> a set of diagonal bands. How can random lines have a pattern? Can
>> anyone explain? When I discard a line, I generate a new random line
>> until is it short enough - so how can it not be random?
>> Win XP & VB 2008 Express. Thanks.
>> --------------------------
>> Imports System
>> Imports System.Drawing
>> Imports Microsoft.VisualBasic
>> Imports Microsoft.VisualBasic.VBMath
>> Imports Microsoft.VisualBasic.PowerPacks
>> Public Class Form1
>>    Dim rec As New RectangleShape
>>    Dim arx(5000, 2) As Integer
>>    Dim ary(5000, 2) As Integer
>>    Public Sub New()
>>        InitializeComponent()
>>        Randomize()
>>        Me.rec.Left = 300
>>        Me.rec.Top = 2
>>        Me.rec.Width = 900
>>        Me.rec.Height = 900
>>        For n = 0 To 4999
>>            arx(n, 0) = arx(n, 1) = ary(n, 0) = ary(n, 1) = 0
>>        Next
>>    End Sub
>>    Private Sub Form1_Paint(ByVal sender As Object, ByVal e As
>> System.Windows.Forms.PaintEventArgs) Handles Me.Paint
>>        PGr()
>>    End Sub
>>    Private Sub PGr()
>>        Dim e As Graphics
>>        e = Me.CreateGraphics
>>        e.FillRectangle(Brushes.White, rec.Left, rec.Top, rec.Width,
>> rec.Height)
>>        For n = 0 To 4999
>>            e.DrawLine(Pens.Black, rec.Left + arx(n, 0), rec.Top +
>> ary(n, 0), _
>>                       rec.Left + arx(n, 1), rec.Top + ary(n, 1))
>>        Next
>>    End Sub
>>    Private Sub ReP_Click(ByVal sender As Object, ByVal e As
>> System.EventArgs) Handles ReP.Click
>>        Dim Dret As Integer = 0
>>        For n = 0 To 4999
>>            Do
>>                arx(n, 0) = Int(Rnd() * 900)
>>                arx(n, 1) = Int(Rnd() * 900)
>>                ary(n, 0) = Int(Rnd() * 900)
>>                ary(n, 1) = Int(Rnd() * 900)
>>                Dret = Dist(n)
>>            Loop Until Dret = 1
>>        Next
>>        PGr()
>>    End Sub
>>    Private Function Dist(ByVal n As Integer) As Integer
>>        Dim x1, x2, y1, y2, h, h1, h2, size As Double
>>        size = 40
>>        x1 = arx(n, 0)
>>        x2 = arx(n, 1)
>>        h1 = Math.Pow((x1 - x2), 2)
>>        y1 = ary(n, 0)
>>        y2 = ary(n, 1)
>>        h2 = Math.Pow((y1 - y2), 2)
>>        h = h1 + h2
>>        h = Math.Sqrt(h)
>>        If h > size Then Return 0
>>        Return 1
>>    End Function
>>    Private Sub Quit_Click(ByVal sender As Object, ByVal e As
>> System.EventArgs) Handles Quit.Click
>>        End
>>    End Sub
>> End Class
>>
>
>
>I would recommend not using Rnd().  Instead create an instance of Random,
>and use it.  I believe after this change you will see what your are trying
>to get.  So my code looks like the following mods:
>
>public class Form1
>...
>  Dim r as New Random
>...
>  Private Sub ReP_Click(...
>  ...
>    arx(n, 0) = CInt(r.NextDouble() * 900.0)
>    arx(n, 1) = CInt(r.NextDouble() * 900.0)
>    ary(n, 0) = CInt(r.NextDouble() * 900.0)
>    ary(n, 1) = CInt(r.NextDouble() * 900.0)
>  ...
>
>
>I cannot address why Rnd() does what you are seeing, because I don't use
>Rnd().
>
>You also might consider generating point 2 (arx(n,1) and ary(n,1)) by using
>a random distance less than your desired size and a random angle.  This will
>save the loopy logic testing whether your random line works.  Your random
>line generated by using a distance and angle will always be less than the
>desired size.  You would have to check for points off the graphics area of
>course, but that should be an easier check.