Apache Pig - LOG()

The LOG() function of Pig Latin is used to calculate the natural logarithm (base e) value of a given expression.

grunt> LOG(expression)

Example

Assume that there is a file named math.txt in the HDFS directory /pig_data/. This file contains integer and floating point values as shown below.

math.txt

5 
16 
9 
2.5 
5.9 
3.1 

And, we have loaded this file into Pig with a relation named math_data as shown below.

grunt> math_data = LOAD 'hdfs://localhost:9000/pig_data/math.txt' USING PigStorage(',')
   as (data:float);

Let us now calculate the log values of the contents of the math.txt file using LOG() function as shown below.

grunt> log_data = foreach math_data generate (data),LOG(data);

The above statement stores the result in the relation named log_data. Verify the contents of the relation using the Dump operator as shown below.

grunt> Dump log_data;
  
(5.0,1.6094379124341003) 
(16.0,2.772588722239781) 
(9.0,2.1972245773362196) 
(2.5,0.9162907318741551) 
(5.9,1.774952367075645) 
(3.1,1.1314020807274126)