In C#, Math.Log() is a Math 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 Math.Log() method as follows:
CSharp
Example:
CSharp
- Math.Log(Double) Method
- Math.Log(Double, Double) Method
Math.Log(Double) Method
This method is used to return the natural (base e) logarithm of a specified number. Syntax:public static double Log(double val)Parameter:
val: It is the specified number whose natural (base e) logarithm to be calculated and its type is System.Double.Return Value: Returns the natural logarithm of val and its type is System.Double. Note: Parameter val 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 loge(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.
// C# program to demonstrate working
// of Math.Log(Double) method
using System;
class Geeks {
// Main Method
public static void Main(String[] args)
{
// double values whose logarithm
// to be calculated
double a = 4.55;
double b = 0;
double c = -2.45;
double nan = Double.NaN;
double positiveInfinity = Double.PositiveInfinity;
double negativeInfinity = Double.NegativeInfinity;
// Input is positive number so output
// will be logarithm of number
Console.WriteLine(Math.Log(a));
// positive zero as argument, so output
// will be -Infinity
Console.WriteLine(Math.Log(b));
// Input is negative number so output
// will be NaN
Console.WriteLine(Math.Log(c));
// Input is NaN so output
// will be NaN
Console.WriteLine(Math.Log(nan));
// Input is PositiveInfinity so output
// will be Infinity
Console.WriteLine(Math.Log(positiveInfinity));
// Input is NegativeInfinity so output
// will be NaN
Console.WriteLine(Math.Log(negativeInfinity));
}
}
Output:
1.51512723296286 -Infinity NaN NaN Infinity NaN
Math.Log(Double, Double) Method
This method is used to return the logarithm of a specified number in a specified base. Syntax:public static double Log(double val, double base)Parameter:
val: It is the specified number whose logarithm to be calculated and its type is System.Double. base: It is the base of the logarithm of type System.Double.Return Value: It returns the logarithm of val and its type is System.Double. 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 |
// C# program to demonstrate working
// of Math.Log(Double, Double) method
using System;
class Geeks {
// Main Method
public static void Main(String[] args)
{
// Here val = 1.3 and base is 0.3 then
// output will be logarithm of given value
Console.WriteLine(Math.Log(1.3, 0.3));
// Here val is 0.5 and base > 1 then output
// will be -0.5
Console.WriteLine(Math.Log(0.5, 4));
// Here val is 0.7 and base = 1 then output
// will be NaN
Console.WriteLine(Math.Log(0.7, 1));
// Here val is 0.7 and base is NaN then output
// will be NaN
Console.WriteLine(Math.Log(0.7, Double.NaN));
}
}
Output:
References:
-0.217915440884381 -0.5 NaN NaN
