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What is LOG() function?

  • In mathematics, the logarithm is the inverse operation to exponentiation, just as division is the inverse of multiplication and vice versa.
  • That means the logarithm of a number is the exponent to which another fixed number, the base, must be raised to produce that number.
  • In simple cases the logarithm counts factors in multiplication.
  • For example, the base 10 logarithm of 1000 is 3, as 10 to the power 3 is 1000 (1000 = 10 × 10 × 10 = 10^3); 10 is used as a factor three times.
 Apache Pig Log

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LOG() function in Apache Pig

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


grunt> LOG(expression)


  • Ensure that we have a file named wikitechy_math.txt in the HDFS directory /pig_data/.
  • This file contains integer and floating point values as given below.


  • You have loaded this file into Pig with a relation named math_data as given below.
grunt> math_data = LOAD 'hdfs://localhost:9000/pig_data/wikitechy_math.txt' USING PigStorage(',')
   as (data:float);
  • Now calculate the log values of the contents of the wikitechy_math.txtfile using LOG() function as given below.
grunt> log_data = foreach math_data generate (data),LOG(data);


  • Now verify the contents of the relation using the Dump operator as given below.
grunt> Dump log_data;


  • The above statement stores the result in the relation named log_data.

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