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C# / .NET - Math.Log() method example

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Created by:

Mohammad-Oneal

327

The Math.Log() method returns the natural logarithm (base e) of a number.

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using System;
​
public class Program
{
    public static void Main(string[] args) 
    {
        // Natural logarithm (logarithm with base e):
        //                           x            y
        Console.WriteLine( Math.Log( 1    ) ); // 0
        Console.WriteLine( Math.Log( 7    ) ); // 1.9459101490553132
        Console.WriteLine( Math.Log( 10   ) ); // 2.3025850929940460
        Console.WriteLine( Math.Log( 100  ) ); // 4.6051701859880920
        Console.WriteLine( Math.Log( 1000 ) ); // 6.9077552789821370
​
        Console.WriteLine( Math.Log( -1                      ) ); // NaN
        Console.WriteLine( Math.Log(  0                      ) ); // -∞ / -Infinity
        Console.WriteLine( Math.Log( Double.PositiveInfinity ) ); //  ∞ / +Infinity
​
        Console.WriteLine( Math.E ); // 2.718281828459045
​
        // Logarithm with custom base is placed in the below example.
    }
}

The Math.Log() method is presented on the following chart:

Math.Log(x) function visualization - C# Math Object.

1. Documentation

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Syntax	xxxxxxxxxx 1 namespace System 2 { 3 public static class Math 4 { 5 // ... 6 public static double Log(double a, double newBase) { ... } 7 public static double Log(double d) { ... } 8 // ... 9 } 10 }
Parameters	`a`, `d` - double value in the range `0` to `+Infinitive` (primitive value). `newBase` - logarithm base.
Result	`number` value calculated as ln(x) mathematical function (primitive value). If `x` is negative it returns `NaN`. If `x` is equal to `0` it returns `-Infinity`. If `x` is equal to `+Infinity` it returns `-Infinity`.
Description	`Log` is a static method that takes one parameter and returns an approximation of the ln(x) function (natural logarithm function - logarithm with base `e`).

2. Logarithm with custom base example

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This example shows a logarithmic function calculation with its own base.

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using System;
​
public class Program
{
    static double calculateLogarithm(double logBase, double x) 
    {
        double a = Math.Log(x);     
        double b = Math.Log(logBase);
​
        return a / b;
    }
​
    public static void Main(string[] args) 
    {
        // Logarithm with custom base:
        //                                    base     x               y
        Console.WriteLine( calculateLogarithm( 2,      2      ) ); //  1
        Console.WriteLine( calculateLogarithm( 2,      4      ) ); //  2
        Console.WriteLine( calculateLogarithm( Math.E, Math.E ) ); //  1
        Console.WriteLine( calculateLogarithm( 3,      9      ) ); //  2
        Console.WriteLine( calculateLogarithm( 3,      81     ) ); //  4
        Console.WriteLine( calculateLogarithm( 10,     10     ) ); //  1
    }
}