Logarithmic Math functions

 

The logarithmic outputs can be easily generated in java using simpler math functions. If you want to know more about Basic Math functions in Java, do check HERE.

Math.log()

This math function outputs the logarithmic value of the input variable.

The input can be of any data type like byte, short, int, long, float and double. 

class java {
    public static void main(String args[]) {
        //Declaring variables
        byte p = 112;
        short q=3200;
        int r=21129;
        long s=2911143;
        float x=11.29f;
        double y=11.29143;
        //Logarithmic outputs
        System.out.println(Math.log(p));
        System.out.println(Math.log(q));
        System.out.println(Math.log(r));
        System.out.println(Math.log(s));
        System.out.println(Math.log(x));
        System.out.println(Math.log(y));
    }
}

 Output

Math.log10()

This Math function returns the base 10 logarithmic value of the input variable. This function is also applicable to all primitive Data types.

class java {
    public static void main(String args[]) {
        //Declaring variables
        byte p = 112;
        short q=3200;
        int r=21129;
        long s=2911143;
        float x=11.29f;
        double y=11.29143;
        //Logarithmic base 10 outputs
        System.out.println(Math.log10(p));
        System.out.println(Math.log10(q));
        System.out.println(Math.log10(r));
        System.out.println(Math.log10(s));
        System.out.println(Math.log10(x));
        System.out.println(Math.log10(y));
    }
}

 Output

Math.log1p(x)

This logarithmic function is quite interesting and different. It generates different outputs depending on the case under which it follows:

Case (i) Positive input

When the input is a positive variable and when this log1p operation is applied, it results in positive logarithmic output.

Case (ii) Negative input

When the input is Not a Number (NaN) or a negative variable, the output is also NaN.

Case (iii) Input = -1

When the input is -1, the output becomes a negative infinity value.

Case (iv) Input = Infinity

When the input is positive infinity (1.0/0), the output is Infinite and if the input is a negative infinity value (-1.0/0), the output is NaN.

Case (v) Input =0

When the input applied to the log1p function is 0, the output is 0 and in case of -0, the output is also -0.

class java {
    public static void main(String args[]) {
        //Declaring variables
        byte p = 112;
        short q=-3200;
        int r=-1;
        double x=1.0/0;
        double y=0.0;
        double z=-0.0;
        //Log1p outputs
        System.out.println("Output for positive input");
        System.out.println(Math.log1p(p));
        System.out.println("Output for negative input");
        System.out.println(Math.log1p(q));
        System.out.println("Output for Input= -1");
        System.out.println(Math.log1p(r));
        System.out.println("Output for infinity input");
        System.out.println(Math.log1p(x));
        System.out.println("Output for positive 0");
        System.out.println(Math.log1p(y));
        System.out.println("Output for negative 0");
        System.out.println(Math.log1p(z));
    }
}

 Output

Math.exp(x)

As the name suggests, this math function returns the exponential value of the input variable.

Case	Input	Output
(i)	Positive/ Negative variable	e^x
(ii)	Positive Infinity	Infinity
(iii)	Negative Infinity	0
(iv)	Positive/ Negative 0/ NaN	1

 

class java {
    public static void main(String args[]) {
        //Declaring variables
        byte p = 112;
        short q=-34;
        double x=1.0/0;
        double x1=-1.0/0;
        double y=0.0;
        double z=-0.0;
        double z1=0.0/0;
        //Log1p outputs
        System.out.println("Output for positive input");
        System.out.println(Math.exp(p));
        System.out.println("Output for negative input");
        System.out.println(Math.exp(q));
        System.out.println("Output for Positive infinity");
        System.out.println(Math.exp(x));
        System.out.println("Output for Negative infinity");
        System.out.println(Math.exp(x1));
        System.out.println("Output for positive 0");
        System.out.println(Math.exp(y));
        System.out.println("Output for negative 0");
        System.out.println(Math.exp(z));
        System.out.println("Output when input is NaN");
        System.out.println(Math.exp(z));
    }
}

 Output

Math.expm1()

The following outputs are generated for these input cases stated below:

Case	Input	Output
(i)	Positive/ Negative	(e^x)-1 ((exponential(x)-1)
(ii)	Positive Infinity	Infinity
(iii)	Negative Infinity	-1
(iv)	Positive zero	0
(v)	Negative zero/ NaN	-0

 

class java {
    public static void main(String args[]) {
        //Declaring variables
        double p = 112;
        short q=-34;
        double x=1.0/0;
        double x1=-1.0/0;
        double y=0.0;
        double z=-0.0;
        double z1=0.0/0;
        //Log1p outputs
        System.out.println("Output for positive input");
        System.out.println(Math.expm1(p));
        System.out.println("Output for negative input");
        System.out.println(Math.expm1(q));
        System.out.println("Output for Positive infinity");
        System.out.println(Math.expm1(x));
        System.out.println("Output for Negative infinity");
        System.out.println(Math.expm1(x1));
        System.out.println("Output for positive 0");
        System.out.println(Math.expm1(y));
        System.out.println("Output for negative 0");
        System.out.println(Math.expm1(z));
        System.out.println("Output when input is NaN");
        System.out.println(Math.expm1(z));
    }
}

 Output

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