com.google.cloud.dataflow.sdk.transforms

Class Mean

java.lang.Object

com.google.cloud.dataflow.sdk.transforms.Mean

public class Mean
extends java.lang.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());
  

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Mean.MeanFn<N extends java.lang.Number> A Combine.CombineFn that computes the arithmetic mean (a.k.a.

Constructor Summary

Constructors

Constructor and Description
Mean()

Method Summary

Methods

Modifier and Type	Method and Description
static <N extends java.lang.Number> Combine.Globally<N,java.lang.Double>	globally() Returns a PTransform that takes an input PCollection<N> 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,N extends java.lang.Number> Combine.PerKey<K,N,java.lang.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

Constructor Detail

Mean

public Mean()

Method Detail

globally

public static <N extends java.lang.Number> Combine.Globally<N,java.lang.Double> globally()

Returns a PTransform that takes an input PCollection<N> 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:

N - the type of the Numbers being combined

perKey

public static <K,N extends java.lang.Number> Combine.PerKey<K,N,java.lang.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

N - the type of the Numbers being combined