Random.NextDouble Method
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Updated: October 2010
Returns a random number between 0.0 and 1.0.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Overridable Function NextDouble As Double
public virtual double NextDouble()
Return Value
Type: System.Double
A double-precision floating point number greater than or equal to 0.0, and less than 1.0.
Examples
The following example uses the NextDouble method to generate sequences of random doubles.
' Example of the Random class constructors and Random.NextDouble( )
' method.
Imports System.Threading
Module Example
' Generate random numbers from the specified Random object.
Sub RunIntNDoubleRandoms(ByVal outputBlock As System.Windows.Controls.TextBlock, _
ByVal randObj As Random)
' Generate the first six random integers.
Dim j As Integer
For j = 0 To 5
outputBlock.Text &= String.Format(" {0,10} ", randObj.Next())
Next j
outputBlock.Text &= vbCrLf
' Generate the first six random doubles.
For j = 0 To 5
outputBlock.Text &= String.Format(" {0:F8} ", randObj.NextDouble())
Next j
outputBlock.Text &= vbCrLf
End Sub
' Create a Random object with the specified seed.
Sub FixedSeedRandoms(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal seed As Integer)
outputBlock.Text &= String.Format(vbCrLf & _
"Random numbers from a Random object with " & _
"seed = {0}:", seed) & vbCrLf
Dim fixRand As New Random(seed)
RunIntNDoubleRandoms(outputBlock, fixRand)
End Sub
' Create a random object with a timer-generated seed.
Sub AutoSeedRandoms(ByVal outputBlock As System.Windows.Controls.TextBlock)
' Wait to allow the timer to advance.
Thread.Sleep(1)
outputBlock.Text &= String.Format(vbCrLf & _
"Random numbers from a Random object " & _
"with an auto-generated seed:") & vbCrLf
Dim autoRand As New Random()
RunIntNDoubleRandoms(outputBlock, autoRand)
End Sub
Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
outputBlock.Text &= String.Format( _
"This example of the Random class constructors " & _
"and Random.NextDouble( ) " & vbCrLf & _
"generates the following output." & vbCrLf) & vbCrLf
outputBlock.Text &= String.Format("Create Random " & _
"objects, and then generate and display six " & _
"integers and " & vbCrLf & "six doubles from each.") & vbCrLf
FixedSeedRandoms(outputBlock, 123)
FixedSeedRandoms(outputBlock, 123)
FixedSeedRandoms(outputBlock, 456)
FixedSeedRandoms(outputBlock, 456)
AutoSeedRandoms(outputBlock)
AutoSeedRandoms(outputBlock)
AutoSeedRandoms(outputBlock)
End Sub
End Module
' This example of the Random class constructors and Random.NextDouble( )
' generates the following output.
'
' Create Random objects, and then generate and display six integers and
' six doubles from each.
'
' Random numbers from a Random object with seed = 123:
' 2114319875 1949518561 1596751841 1742987178 1586516133 103755708
' 0.01700087 0.14935942 0.19470390 0.63008947 0.90976122 0.49519146
'
' Random numbers from a Random object with seed = 123:
' 2114319875 1949518561 1596751841 1742987178 1586516133 103755708
' 0.01700087 0.14935942 0.19470390 0.63008947 0.90976122 0.49519146
'
' Random numbers from a Random object with seed = 456:
' 2044805024 1323311594 1087799997 1907260840 179380355 120870348
' 0.21988117 0.21026556 0.39236514 0.42420498 0.24102703 0.47310170
'
' Random numbers from a Random object with seed = 456:
' 2044805024 1323311594 1087799997 1907260840 179380355 120870348
' 0.21988117 0.21026556 0.39236514 0.42420498 0.24102703 0.47310170
'
' Random numbers from a Random object with an auto-generated seed:
' 1920831619 1346865774 2006582766 1968819760 332463652 110770792
' 0.71326689 0.50383335 0.50446082 0.66312569 0.94517193 0.58059287
'
' Random numbers from a Random object with an auto-generated seed:
' 254927927 1205531663 1984850027 110020849 1438111494 1697714106
' 0.19383387 0.52067738 0.74162783 0.35063667 0.31247720 0.38773733
'
' Random numbers from a Random object with an auto-generated seed:
' 736507882 1064197552 1963117288 398705585 396275689 1137173773
' 0.67440084 0.53752140 0.97879483 0.03814764 0.67978248 0.19488178
// Example of the Random class constructors and Random.NextDouble( )
// method.
using System;
using System.Threading;
public class Example
{
// Generate random numbers from the specified Random object.
static void RunIntNDoubleRandoms(System.Windows.Controls.TextBlock outputBlock, Random randObj)
{
// Generate the first six random integers.
for (int j = 0; j < 6; j++)
outputBlock.Text += String.Format(" {0,10} ", randObj.Next());
outputBlock.Text += "\n";
// Generate the first six random doubles.
for (int j = 0; j < 6; j++)
outputBlock.Text += String.Format(" {0:F8} ", randObj.NextDouble());
outputBlock.Text += "\n";
}
// Create a Random object with the specified seed.
static void FixedSeedRandoms(System.Windows.Controls.TextBlock outputBlock, int seed)
{
outputBlock.Text += String.Format(
"\nRandom numbers from a Random object with " +
"seed = {0}:", seed) + "\n";
Random fixRand = new Random(seed);
RunIntNDoubleRandoms(outputBlock, fixRand);
}
// Create a random object with a timer-generated seed.
static void AutoSeedRandoms(System.Windows.Controls.TextBlock outputBlock)
{
// Wait to allow the timer to advance.
Thread.Sleep(1);
outputBlock.Text += String.Format(
"\nRandom numbers from a Random object " +
"with an auto-generated seed:") + "\n";
Random autoRand = new Random();
RunIntNDoubleRandoms(outputBlock, autoRand);
}
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
outputBlock.Text += String.Format(
"This example of the Random class constructors and " +
"Random.NextDouble( ) \n" +
"generates the following output.\n") + "\n";
outputBlock.Text += String.Format(
"Create Random objects, and then generate and " +
"display six integers and \nsix doubles from each.") + "\n";
FixedSeedRandoms(outputBlock, 123);
FixedSeedRandoms(outputBlock, 123);
FixedSeedRandoms(outputBlock, 456);
FixedSeedRandoms(outputBlock, 456);
AutoSeedRandoms(outputBlock);
AutoSeedRandoms(outputBlock);
AutoSeedRandoms(outputBlock);
}
}
/*
This example of the Random class constructors and Random.NextDouble( )
generates the following output.
Create Random objects, and then generate and display six integers and
six doubles from each.
Random numbers from a Random object with seed = 123:
2114319875 1949518561 1596751841 1742987178 1586516133 103755708
0.01700087 0.14935942 0.19470390 0.63008947 0.90976122 0.49519146
Random numbers from a Random object with seed = 123:
2114319875 1949518561 1596751841 1742987178 1586516133 103755708
0.01700087 0.14935942 0.19470390 0.63008947 0.90976122 0.49519146
Random numbers from a Random object with seed = 456:
2044805024 1323311594 1087799997 1907260840 179380355 120870348
0.21988117 0.21026556 0.39236514 0.42420498 0.24102703 0.47310170
Random numbers from a Random object with seed = 456:
2044805024 1323311594 1087799997 1907260840 179380355 120870348
0.21988117 0.21026556 0.39236514 0.42420498 0.24102703 0.47310170
Random numbers from a Random object with an auto-generated seed:
380213349 127379247 1969091178 1983029819 1963098450 1648433124
0.08824121 0.41249688 0.36445811 0.05637512 0.62702451 0.49595560
Random numbers from a Random object with an auto-generated seed:
861793304 2133528783 1947358439 124230908 921262645 1087892791
0.56880819 0.42934091 0.60162512 0.74388610 0.99432979 0.30310005
Random numbers from a Random object with an auto-generated seed:
1343373259 1992194672 1925625700 412915644 2026910487 527352458
0.04937517 0.44618494 0.83879212 0.43139707 0.36163507 0.11024451
*/
The following example calls the NextDouble method to generate 100 random numbers and displays their frequency distribution.
Module Example
Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim frequency(9) As Integer
Dim number As Double
Dim rnd As New Random()
For ctr As Integer = 0 To 99
number = rnd.NextDouble()
frequency(CInt(Math.Floor(number * 10))) += 1
Next
outputBlock.Text &= "Distribution of Random Numbers:" & vbCrLf
For ctr As Integer = frequency.GetLowerBound(0) To frequency.GetUpperBound(0)
outputBlock.Text += String.Format("0.{0}0-0.{0}9 {1}", ctr, frequency(ctr)) & vbCrLf
Next
End Sub
End Module
' The following example displays output similar to the following:
' Distribution of Random Numbers:
' 0.00-0.09 16
' 0.10-0.19 8
' 0.20-0.29 8
' 0.30-0.39 11
' 0.40-0.49 9
' 0.50-0.59 6
' 0.60-0.69 13
' 0.70-0.79 6
' 0.80-0.89 9
' 0.90-0.99 14
using System;
public class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
int[] frequency = new int[10];
double number;
Random rnd = new Random();
for (int ctr = 0; ctr <= 99; ctr++)
{
number = rnd.NextDouble();
frequency[(int)Math.Floor(number * 10)]++;
}
outputBlock.Text += "Distribution of Random Numbers:" + "\n";
for (int ctr = frequency.GetLowerBound(0); ctr <= frequency.GetUpperBound(0); ctr++)
outputBlock.Text += String.Format("0.{0}0-0.{0}9 {1}", ctr, frequency[ctr]) + "\n";
}
}
// The following example displays output similar to the following:
// Distribution of Random Numbers:
// 0.00-0.09 16
// 0.10-0.19 8
// 0.20-0.29 8
// 0.30-0.39 11
// 0.40-0.49 9
// 0.50-0.59 6
// 0.60-0.69 13
// 0.70-0.79 6
// 0.80-0.89 9
// 0.90-0.99 14
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0
XNA Framework
Supported in: Xbox 360, Windows Phone OS 7.0
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.
Change History
Date |
History |
Reason |
|---|---|---|
October 2010 |
Added a second example. |
Customer feedback. |