org.datavec.api.transform.reduce

Class Reducer

java.lang.Object

org.datavec.api.transform.reduce.Reducer

All Implemented Interfaces:

Serializable, IAssociativeReducer

public class Reducer
extends Object
implements IAssociativeReducer

A Reducer is used to take a set of examples and reduce them. The idea: suppose you have a large number of columns, and you want to combine/reduce the values in each column.
Reducer allows you to specify different reductions for differently for different columns: min, max, sum, mean etc. See Reducer.Builder and ReduceOp for the full list.
Note this supports executing multipe reducitons per column: simply call the Builder with Xcolumn() repeatedly on the same column, or use Reducer.Builder.multipleOpColmumns(List, String...)}

Uses are: (1) Reducing examples by a key (2) Reduction operations in time series (windowing ops, etc)

Author:

Alex Black

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Reducer.Builder
static class	Reducer.ConditionalReduction

Constructor Summary

Constructors

Constructor and Description
Reducer(List<String> keyColumns, ReduceOp defaultOp, Map<String,List<ReduceOp>> opMap, Map<String,AggregableColumnReduction> customReductions, Map<String,Reducer.ConditionalReduction> conditionalReductions, Set<String> ignoreInvalidInColumns)

Method Summary

Modifier and Type	Method and Description
IAggregableReduceOp<List<Writable>,List<Writable>>	aggregableReducer() An aggregation that has the property that reduce(List(reduce(List(l1, l2)), l3)) = reduce(List(l1, reduce(List(l2, l3)))
Schema	getInputSchema()
List<String>	getKeyColumns()
void	setInputSchema(Schema schema)
String	toString()
Schema	transform(Schema schema) Get the output schema, given the input schema

Methods inherited from class java.lang.Object

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

Constructor Detail

Reducer

public Reducer(List<String> keyColumns,
               ReduceOp defaultOp,
               Map<String,List<ReduceOp>> opMap,
               Map<String,AggregableColumnReduction> customReductions,
               Map<String,Reducer.ConditionalReduction> conditionalReductions,
               Set<String> ignoreInvalidInColumns)

Method Detail

setInputSchema

public void setInputSchema(Schema schema)

Specified by:

setInputSchema in interface IAssociativeReducer

getInputSchema

public Schema getInputSchema()

Specified by:

getInputSchema in interface IAssociativeReducer

Returns:

getKeyColumns

public List<String> getKeyColumns()

Specified by:

getKeyColumns in interface IAssociativeReducer

Returns:

transform

public Schema transform(Schema schema)

Get the output schema, given the input schema

Specified by:

transform in interface IAssociativeReducer

Returns:

aggregableReducer

public IAggregableReduceOp<List<Writable>,List<Writable>> aggregableReducer()

Description copied from interface: IAssociativeReducer

An aggregation that has the property that reduce(List(reduce(List(l1, l2)), l3)) = reduce(List(l1, reduce(List(l2, l3)))

Specified by:

aggregableReducer in interface IAssociativeReducer

Returns:

toString

public String toString()

Overrides:

toString in class Object