org.grouplens.lenskit.eval.metrics.predict

Class MAEPredictMetric

java.lang.Object

org.grouplens.lenskit.eval.metrics.AbstractMetric<MAEPredictMetric.Context,MAEPredictMetric.AggregateResult,MAEPredictMetric.UserResult>

org.grouplens.lenskit.eval.metrics.predict.MAEPredictMetric

All Implemented Interfaces:

Closeable, AutoCloseable, Metric<MAEPredictMetric.Context>

public class MAEPredictMetric
extends AbstractMetric<MAEPredictMetric.Context,MAEPredictMetric.AggregateResult,MAEPredictMetric.UserResult>

Evaluate a recommender's predictions by Mean Absolute Error. In general, prefer RMSE (RMSEPredictMetric) to MAE.

This evaluator computes two variants of MAE. The first is by-rating, where the absolute error is averaged over all predictions. The second is by-user, where the MAE is computed per-user and then averaged over all users.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MAEPredictMetric.AggregateResult
class	MAEPredictMetric.Context
static class	MAEPredictMetric.UserResult

Constructor Summary

Constructors

Constructor and Description
MAEPredictMetric()

Method Summary

Modifier and Type	Method and Description
MAEPredictMetric.Context	createContext(Attributed algo, TTDataSet ds, Recommender rec) Create the context for an experimental condition (algorithm/data set pair).
MAEPredictMetric.UserResult	doMeasureUser(TestUser user, MAEPredictMetric.Context context) Measure a user with typed results.
protected MAEPredictMetric.AggregateResult	getTypedResults(MAEPredictMetric.Context context) Get the typed results from an accumulator.

Methods inherited from class org.grouplens.lenskit.eval.metrics.AbstractMetric

close, getColumnLabels, getPrefix, getResults, getSuffix, getUserColumnLabels, measureUser

Methods inherited from class java.lang.Object

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

Constructor Detail

MAEPredictMetric

public MAEPredictMetric()

Method Detail

createContext

public MAEPredictMetric.Context createContext(Attributed algo,
                                              TTDataSet ds,
                                              Recommender rec)

Description copied from interface: Metric

Create the context for an experimental condition (algorithm/data set pair).

Parameters:

algo - The algorithm.

ds - The data set.

rec - The LensKit recommender, if applicable. This can be null for an external algorithm that does not provide a LensKit recommender.

Returns:

The accumulator. This will be passed to Metric.measureUser(TestUser, Object). If the metric does not accumulate any results, this method can return null.

doMeasureUser

public MAEPredictMetric.UserResult doMeasureUser(TestUser user,
                                                 MAEPredictMetric.Context context)

Description copied from class: AbstractMetric

Measure a user with typed results.

Specified by:

doMeasureUser in class AbstractMetric<MAEPredictMetric.Context,MAEPredictMetric.AggregateResult,MAEPredictMetric.UserResult>

Parameters:

user - The user to measure.

context - The context.

Returns:

The results of measuring the user, or null to emit NAs for the user.

getTypedResults

protected MAEPredictMetric.AggregateResult getTypedResults(MAEPredictMetric.Context context)

Description copied from class: AbstractMetric

Get the typed results from an accumulator.

Specified by:

getTypedResults in class AbstractMetric<MAEPredictMetric.Context,MAEPredictMetric.AggregateResult,MAEPredictMetric.UserResult>

Parameters:

context - The context.

Returns:

The results accumulated for this experiment, or null to emit NAs.