CrossValidationPartitioner (Apache OpenNLP Tools 2.1.1 API)

java.lang.Object
- opennlp.tools.util.eval.CrossValidationPartitioner<E>

```
public class CrossValidationPartitioner<E>
extends Object
```
Provides access to training and test partitions for n-fold cross validation.
Cross validation is used to evaluate the performance of a classifier when only training data is available. The training set is split into n parts and the training / evaluation is performed n times on these parts. The training partition always consists of n - 1 parts and one part is used for testing.
To use the CrossValidationPartitioner a client iterates over the n stream. Each CrossValidationPartitioner.TrainingSampleStream represents one partition and is used first for training and afterwards for testing. The CrossValidationPartitioner.TestSampleStream can be obtained via the CrossValidationPartitioner.TrainingSampleStream.getTestSampleStream() method.

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static class`	`CrossValidationPartitioner.TrainingSampleStream<E>`	The `CrossValidationPartitioner.TrainingSampleStream` which iterates over all training elements.

Constructor Summary

Constructors
Constructor	Description
`CrossValidationPartitioner(Collection<E> elements, int numberOfPartitions)`	Initializes `CrossValidationPartitioner` instance.
`CrossValidationPartitioner(ObjectStream<E> inElements, int numberOfPartitions)`	Initializes `CrossValidationPartitioner` instance.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`hasNext()`	Checks if there are more partitions available.
`CrossValidationPartitioner.TrainingSampleStream<E>`	`next()`	Retrieves the next training and test partitions.
`String`	`toString()`

Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - CrossValidationPartitioner
```
public CrossValidationPartitioner(ObjectStream<E> inElements,
                                  int numberOfPartitions)
```
    Initializes CrossValidationPartitioner instance.
    
    Parameters:
    
    inElements - The ObjectStream that provides the elements.
    
    numberOfPartitions - The number of partitions. Must be greater than 0.
  - CrossValidationPartitioner
```
public CrossValidationPartitioner(Collection<E> elements,
                                  int numberOfPartitions)
```
    Initializes CrossValidationPartitioner instance.
    
    Parameters:
    
    elements - A Collection that provides the elements.
    
    numberOfPartitions - The number of partitions. Must be greater than 0.
- Method Detail
  - hasNext
```
public boolean hasNext()
```
    Checks if there are more partitions available.
  - next
```
public CrossValidationPartitioner.TrainingSampleStream<E> next()
                                                        throws IOException
```
    Retrieves the next training and test partitions.
    
    Throws:
    
    IOException
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object