Export (0) Print
Expand All
This topic has not yet been rated - Rate this topic

Math.Log10 Method

Returns the base 10 logarithm of a specified number.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

'Declaration
Public Shared Function Log10 ( _
	d As Double _
) As Double
'Usage
Dim d As Double
Dim returnValue As Double

returnValue = Math.Log10(d)
public static double Log10 (
	double d
)
public static function Log10 (
	d : double
) : double

Parameters

d

A number whose logarithm is to be found.

Return Value

Sign of d

Returns

Positive

The base 10 log of d; that is, log 10d.

Zero

NegativeInfinity

Negative

NaN

If d is equal to NaN, this method returns NaN. If d is equal to PositiveInfinity, this method returns PositiveInfinity.

Parameter d is specified as a base 10 number.

The following example uses Log10 to evaluate certain logarithmic identities for selected values.

' Example for the Math.Log( Double, Double )and Math.Log10( Double ) methods.
Imports System
Imports Microsoft.VisualBasic

Module LogDDLog10
       
    Sub Main()
        Console.WriteLine( _
            "This example of Math.Log( Double, Double ) " + _
            "and Math.Log10( Double )" & vbCrLf & _
            "generates the following output." & vbCrLf)
        Console.WriteLine( _
            "Evaluate these identities with " & _
            "selected values for X and B (base):")
        Console.WriteLine("   log(B)[X] = 1 / log(X)[B]")
        Console.WriteLine("   log(B)[X] = log(10)[X] / log(10)[B]")
        Console.WriteLine("   log(B)[X] = log(B)[10] * log(10)[X]")
          
        UseBaseAndArg(0.1, 1.2)
        UseBaseAndArg(1.2, 4.9)
        UseBaseAndArg(4.9, 9.9)
        UseBaseAndArg(9.9, 0.1)
    End Sub 'Main
       
    ' Evaluate logarithmic identities that are functions of two arguments.
    Sub UseBaseAndArg(argB As Double, argX As Double)

        ' Evaluate log(B)[X] = 1 / log(X)[B].
        Console.WriteLine( _
            vbCrLf & "                   Math.Log({1}, {0}) = {2:E16}" + _
            vbCrLf & "             1.0 / Math.Log({0}, {1}) = {3:E16}", _
            argB, argX, Math.Log(argX, argB), _
            1.0 / Math.Log(argB, argX))
          
        ' Evaluate log(B)[X] = log(10)[X] / log(10)[B].
        Console.WriteLine( _
            "    Math.Log10({1}) / Math.Log10({0}) = {2:E16}", _
            argB, argX, Math.Log10(argX) / Math.Log10(argB))
          
        ' Evaluate log(B)[X] = log(B)[10] * log(10)[X].
        Console.WriteLine( _
            "Math.Log(10.0, {0}) * Math.Log10({1}) = {2:E16}", _
            argB, argX, Math.Log(10.0, argB) * Math.Log10(argX))

    End Sub 'UseBaseAndArg
End Module 'LogDDLog10

' This example of Math.Log( Double, Double ) and Math.Log10( Double )
' generates the following output.
'
' Evaluate these identities with selected values for X and B (base):
'    log(B)[X] = 1 / log(X)[B]
'    log(B)[X] = log(10)[X] / log(10)[B]
'    log(B)[X] = log(B)[10] * log(10)[X]
' 
'                    Math.Log(1.2, 0.1) = -7.9181246047624818E-002
'              1.0 / Math.Log(0.1, 1.2) = -7.9181246047624818E-002
'     Math.Log10(1.2) / Math.Log10(0.1) = -7.9181246047624818E-002
' Math.Log(10.0, 0.1) * Math.Log10(1.2) = -7.9181246047624831E-002
' 
'                    Math.Log(4.9, 1.2) = 8.7166610085093179E+000
'              1.0 / Math.Log(1.2, 4.9) = 8.7166610085093161E+000
'     Math.Log10(4.9) / Math.Log10(1.2) = 8.7166610085093179E+000
' Math.Log(10.0, 1.2) * Math.Log10(4.9) = 8.7166610085093179E+000
' 
'                    Math.Log(9.9, 4.9) = 1.4425396251981288E+000
'              1.0 / Math.Log(4.9, 9.9) = 1.4425396251981288E+000
'     Math.Log10(9.9) / Math.Log10(4.9) = 1.4425396251981288E+000
' Math.Log(10.0, 4.9) * Math.Log10(9.9) = 1.4425396251981291E+000
' 
'                    Math.Log(0.1, 9.9) = -1.0043839404494075E+000
'              1.0 / Math.Log(9.9, 0.1) = -1.0043839404494075E+000
'     Math.Log10(0.1) / Math.Log10(9.9) = -1.0043839404494077E+000
' Math.Log(10.0, 9.9) * Math.Log10(0.1) = -1.0043839404494077E+000

// Example for the Math.Log( double, double ) and Math.Log10( double ) methods.
import System.*;

class LogDDLog10
{
    public static void main(String[] args)
    {
        Console.WriteLine(("This example of Math.Log( double, double ) " 
            + "and Math.Log10( double )\n" 
            + "generates the following output.\n"));
        Console.WriteLine(("Evaluate these identities with " 
            + "selected values for X and B (base):"));
        Console.WriteLine("   log(B)[X] == 1 / log(X)[B]");
        Console.WriteLine("   log(B)[X] == log(10)[X] / log(10)[B]");
        Console.WriteLine("   log(B)[X] == log(B)[10] * log(10)[X]");
        UseBaseAndArg(0.1, 1.2);
        UseBaseAndArg(1.2, 4.9);
        UseBaseAndArg(4.9, 9.9);
        UseBaseAndArg(9.9, 0.1);
    } //main
     
    // Evaluate logarithmic identities that are functions of two arguments.
    static void UseBaseAndArg(double argB, double argX)
    {
        // Evaluate log(B)[X] == 1 / log(X)[B].
        Console.WriteLine("\n                   Math.Log({1}, {0}) == {2}" 
            + "\n             1.0 / Math.Log({0}, {1}) == {3}",
            new Object[]{ System.Convert.ToString(argB), 
            System.Convert.ToString(argX),((System.Double)( 
            System.Math.Log(argX, argB))).ToString("E16"), 
            ((System.Double)(1.0 / System.Math.Log(argB, argX)))
            .ToString("E16")});

        // Evaluate log(B)[X] == log(10)[X] / log(10)[B].
        Console.WriteLine("    Math.Log10({1}) / Math.Log10({0}) == {2}", 
            System.Convert.ToString(argB), 
            System.Convert.ToString(argX), 
            ((System.Double)(System.Math.Log10(argX) / 
            System.Math.Log10(argB))).ToString("E16"));

        // Evaluate log(B)[X] == log(B)[10] * log(10)[X].
        Console.WriteLine("Math.Log(10.0, {0}) * Math.Log10({1}) == {2}", 
            System.Convert.ToString(argB), 
            System.Convert.ToString(argX),
            ((System.Double) (System.Math.Log(10.0, argB)
            * System.Math.Log10(argX))).ToString("E16") );
    } //UseBaseAndArg
} //LogDDLog10

/*
This example of Math.Log( double, double ) and Math.Log10( double )
generates the following output.

Evaluate these identities with selected values for X and B (base):
   log(B)[X] == 1 / log(X)[B]
   log(B)[X] == log(10)[X] / log(10)[B]
   log(B)[X] == log(B)[10] * log(10)[X]

                   Math.Log(1.2, 0.1) == -7.9181246047624818E-002
             1.0 / Math.Log(0.1, 1.2) == -7.9181246047624818E-002
    Math.Log10(1.2) / Math.Log10(0.1) == -7.9181246047624818E-002
Math.Log(10.0, 0.1) * Math.Log10(1.2) == -7.9181246047624831E-002

                   Math.Log(4.9, 1.2) == 8.7166610085093179E+000
             1.0 / Math.Log(1.2, 4.9) == 8.7166610085093161E+000
    Math.Log10(4.9) / Math.Log10(1.2) == 8.7166610085093179E+000
Math.Log(10.0, 1.2) * Math.Log10(4.9) == 8.7166610085093179E+000

                   Math.Log(9.9, 4.9) == 1.4425396251981288E+000
             1.0 / Math.Log(4.9, 9.9) == 1.4425396251981288E+000
    Math.Log10(9.9) / Math.Log10(4.9) == 1.4425396251981288E+000
Math.Log(10.0, 4.9) * Math.Log10(9.9) == 1.4425396251981291E+000

                   Math.Log(0.1, 9.9) == -1.0043839404494075E+000
             1.0 / Math.Log(9.9, 0.1) == -1.0043839404494075E+000
    Math.Log10(0.1) / Math.Log10(9.9) == -1.0043839404494077E+000
Math.Log(10.0, 9.9) * Math.Log10(0.1) == -1.0043839404494077E+000
*/

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0
Did you find this helpful?
(1500 characters remaining)
Thank you for your feedback

Community Additions

ADD
Show:
© 2014 Microsoft. All rights reserved.