MathF.Log() Method in C# with Examples

In C#, MathF.Log() is a MathF class method. It is used to return the logarithm of a specified number. This method can be overloaded by changing the number of the arguments passed. There are total 2 methods in the overload list of the MathF.Log() method as follows:

• MathF.Log(Single) Method
• MathF.Log(Single, Single) Method

MathF.Log(Single) Method

This method is used to return the natural (base e) logarithm of a specified number.

Syntax: public static float Log (float x);
Here, x is the specified number whose natural (base e) logarithm to be calculated and its type is System.Single.

Return Value: Returns the natural logarithm of x and its type is System.Single.

Note: Parameter x is always specified as a base 10 number. The return value is depend on the argument passed. Below are some cases:

• If the argument is positive then method will return the natural logarithm or log_e(val).
• If the argument is zero, then the result is NegativeInfinity.
• If the argument is Negative(less than zero) or equal to NaN, then the result is NaN.
• If the argument is PositiveInfinity, then the result is PositiveInfinity.
• If the argument is NegativeInfinity, then the result is NaN.

Example:

// C# program to demonstrate working
// of MathF.Log(Single) method
using System;

class Geeks {

    // Main Method
    public static void Main(String[] args)
    {

        // Single values whose logarithm
        // to be calculated
        float a = 9.78f;
        float b = 0f;
        float c = -4.56f;
        float nan = Single.NaN;
        float positiveInfinity = Single.PositiveInfinity;
        float negativeInfinity = Single.NegativeInfinity;

        // Input is positive number so output
        // will be logarithm of number
        Console.WriteLine(MathF.Log(a));

        // positive zero as argument, so output
        // will be -Infinity
        Console.WriteLine(MathF.Log(b));

        // Input is negative number so output
        // will be NaN
        Console.WriteLine(MathF.Log(c));

        // Input is NaN so output
        // will be NaN
        Console.WriteLine(MathF.Log(nan));

        // Input is PositiveInfinity so output
        // will be Infinity
        Console.WriteLine(MathF.Log(positiveInfinity));

        // Input is NegativeInfinity so output
        // will be NaN
        Console.WriteLine(MathF.Log(negativeInfinity));
    }
}

Output:

2.280339
-Infinity
NaN
NaN
Infinity
NaN

Math.Log(Single, Single) Method

This method is used to return the logarithm of a specified number in a specified base.

Syntax: public static float Log (float x, float y);

Parameters:
x: It is the specified number whose logarithm to be calculated and its type is System.Single.
y: It is the base of the logarithm of type System.Single.

Return Value: It returns the logarithm of x and its type is System.Single.

Note: The return value is always depend on the argument passed. Below table depicts the different cases:

val	base	Returned Value
val > 0	(0 < Base < 1) or(Base > 1)	logbase(val)
val < 0	any value	NaN
any value	base < 0	NaN
val != 1	base = 0	NaN
val != 1	base = +ve Infinity	NaN
val = NaN	any value	NaN
any value	base = NaN	NaN
any value	base = 1	NaN
val = 0	(0 < Base < 1)	+ve Infinity
val = 0	base > 1	-ve Infinity
val = +ve Infinity	(0 < Base < 1)	-ve Infinity
val = +ve Infinity	base > 1	+ve Infinity
val = 1	base = 0	0
val = 1	base = +ve Infinity	0

Example:

// C# program to demonstrate working
// of MathF.Log(Single, Single) method
using System;

class Geeks {

    // Main Method
    public static void Main(String[] args)
    {

        // Here val = 4.4f and base is 0.4f then
        // output will be logarithm of given value
        Console.WriteLine(MathF.Log(4.4f, 0.4f));

        // Here val is 0.5f and base > 1f then output
        // will be -0.5f
        Console.WriteLine(MathF.Log(0.5f, 4f));

        // Here val is 0.9f and base = 1f then output
        // will be NaN
        Console.WriteLine(MathF.Log(0.9f, 1f));

        // Here val is 0.4f and base is NaN then output
        // will be NaN
        Console.WriteLine(MathF.Log(0.4f, Single.NaN));
    }
}

Output:

-1.616959
-0.5
NaN
NaN