Mean (Google Cloud Dataflow SDK 1.9.1 API)

Google Cloud Dataflow SDK for Java, version 1.9.1

Warning: Dataflow SDK 1.x for Java is unsupported as of October 16, 2018. See Migrating from Dataflow SDK 1.x for Java for migration guidance.

Note: If you are using Cloud Dataflow SDK version 2.x, see the Apache Beam API reference documentation.

com.google.cloud.dataflow.sdk.transforms

Class Mean

• java.lang.Object
• • com.google.cloud.dataflow.sdk.transforms.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 Summary

    All Methods Static Methods Concrete Methods 

    Modifier and Type	Method and Description
    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.
    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.

    • Methods inherited from class java.lang.Object

      clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

• • 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