Mean

java.lang.Object
- org.apache.beam.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());
  
```

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static <NumT extends java.lang.Number> Combine.Globally<NumT,java.lang.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 <NumT extends java.lang.Number> Combine.AccumulatingCombineFn<NumT,org.apache.beam.sdk.transforms.Mean.CountSum<NumT>,java.lang.Double>`	`of()` A `Combine.CombineFn` that computes the arithmetic mean (a.k.a.
`static <K,NumT extends java.lang.Number> Combine.PerKey<K,NumT,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

- Method Detail
  - globally
```
public static <NumT extends java.lang.Number> Combine.Globally<NumT,java.lang.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 java.lang.Number> Combine.PerKey<K,NumT,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
    
    NumT - the type of the Numbers being combined
  - of
```
public static <NumT extends java.lang.Number> Combine.AccumulatingCombineFn<NumT,org.apache.beam.sdk.transforms.Mean.CountSum<NumT>,java.lang.Double> of()
```
    A Combine.CombineFn that computes the arithmetic mean (a.k.a. average) of an Iterable of numbers of type N, useful as an argument to Combine.globally(org.apache.beam.sdk.transforms.SerializableFunction<java.lang.Iterable<V>, V>) or Combine.perKey(org.apache.beam.sdk.transforms.SerializableFunction<java.lang.Iterable<V>, V>).
    Returns Double.NaN if combining zero elements.
    
    Type Parameters:
    
    NumT - the type of the Numbers being combined

Class Mean

Method Summary

Methods inherited from class java.lang.Object

Method Detail

globally

perKey

of