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)