Mean (Google Cloud Dataflow SDK 1.9.1 API)

Google Cloud Dataflow SDK for Java, version 1.9.1

com.google.cloud.dataflow.sdk.transforms

Class Mean


  • public class Mean
extends Object
    PTransforms for computing the arithmetic mean (a.k.a. average) of the elements in a PCollection, or the mean of the values associated with each key in a PCollection of KVs.

    Example 1: get the mean of a PCollection of Longs. 

     
 PCollection<Long> input = ...;
 PCollection<Double> mean = input.apply(Mean.<Long>globally());

    Example 2: calculate the mean of the Integers associated with each unique key (which is of type String). 

     
 PCollection<KV<String, Integer>> input = ...;
 PCollection<KV<String, Double>> meanPerKey =
     input.apply(Mean.<String, Integer>perKey());

    • Method Detail

      • globally

        public static <NumT extends Number> Combine.Globally<NumT,Double> globally()
        Returns a PTransform that takes an input PCollection<NumT> and returns a PCollection<Double> whose contents is the mean of the input PCollection's elements, or 0 if there are no elements.
        Type Parameters:
        NumT - the type of the Numbers being combined

      • perKey

        public static <K,NumT extends Number> Combine.PerKey<K,NumT,Double> perKey()
        Returns a PTransform that takes an input PCollection<KV<K, N>> and returns a PCollection<KV<K, Double>> that contains an output element mapping each distinct key in the input PCollection to the mean of the values associated with that key in the input PCollection.

        See Combine.PerKey for how this affects timestamps and bucketing.

        Type Parameters:
        K - the type of the keys
        NumT - the type of the Numbers being combined