The LOG10() function of Pig Latin is used to calculate the natural logarithm base 10 value of a given expression.
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.
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 log10 values of the contents of the math.txt file using LOG10() function as shown below.
grunt> log_data = foreach math_data generate (data),LOG10(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 log10_data; (5.0,0.6989700043360189) (16.0,1.2041199826559248) (9.0,0.9542425094393249) (2.5,0.3979400086720376) (5.9,0.7708520186620678) (3.1,0.4913616804737727)