reduceByKey

Class: matlab.compiler.mlspark.RDD
Namespace: matlab.compiler.mlspark

Merge the values for each key using an associative reduce function

Syntax

result = reduceByKey(obj,func,numPartitions)


Description

result = reduceByKey(obj,func,numPartitions) merges the values for each key in obj using an associative reduce function func. numPartitions specifies the number of partitions to create in the resulting RDD.

Input Arguments

obj — Input RDD

RDD object

An input RDD, specified as a RDD object.

func — Associative function to be applied

function handle

Associative function to be applied to the elements of the input RDD, specified as a function handle.

Data Types: function_handle

numPartitions — Number of partitions to create

scalar value

Number of partitions to create, specified as a scalar value.

Data Types: double

Output Arguments

result — RDD containing values reduced by key

RDD object

A pipelined RDD containing values reduced by key, returned as a RDD object.

Examples

Reduce Values By Key

%% Connect to Spark
sparkProp = containers.Map({'spark.executor.cores'}, {'1'});
conf = matlab.compiler.mlspark.SparkConf('AppName','myApp', ...
                        'Master','local[1]','SparkProperties',sparkProp);
sc = matlab.compiler.mlspark.SparkContext(conf);

%% reduceByKey
inputRDD = sc.parallelize({'A','B','C','A','B'},2);
redRDD= inputRDD.map(@(x)({x,1})).reduceByKey(@(x,y)(x+y),3);

Version History

Introduced in R2016b