org.grouplens.lenskit.eval.metrics.topn

Class NDCGTopNMetric

java.lang.Object

org.grouplens.lenskit.eval.metrics.AbstractMetric<MeanAccumulator,NDCGTopNMetric.Result,NDCGTopNMetric.Result>

org.grouplens.lenskit.eval.metrics.topn.NDCGTopNMetric

All Implemented Interfaces:

Closeable, AutoCloseable, Metric<MeanAccumulator>

public class NDCGTopNMetric
extends AbstractMetric<MeanAccumulator,NDCGTopNMetric.Result,NDCGTopNMetric.Result>

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	NDCGTopNMetric.Builder
static class	NDCGTopNMetric.Result

Constructor Summary

Constructors

Constructor and Description
NDCGTopNMetric(String pre, String sfx, int listSize, ItemSelector candidates, ItemSelector exclude) Construct a new nDCG Top-N metric.

Method Summary

Modifier and Type	Method and Description
MeanAccumulator	createContext(Attributed algo, TTDataSet ds, Recommender rec) Create the context for an experimental condition (algorithm/data set pair).
NDCGTopNMetric.Result	doMeasureUser(TestUser user, MeanAccumulator context) Measure a user with typed results.
protected String	getPrefix() A prefix to be applied to column names.
protected String	getSuffix() A suffix to be applied to column names.
protected NDCGTopNMetric.Result	getTypedResults(MeanAccumulator context) Get the typed results from an accumulator.

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

close, getColumnLabels, getResults, getUserColumnLabels, measureUser

Methods inherited from class java.lang.Object

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

Constructor Detail

NDCGTopNMetric

public NDCGTopNMetric(String pre,
                      String sfx,
                      int listSize,
                      ItemSelector candidates,
                      ItemSelector exclude)

Construct a new nDCG Top-N metric.

Parameters:

pre - the prefix label for this evaluation, or null for no prefix.

sfx - the suffix label for this evaluation, or null for no suffix.

listSize - The number of recommendations to fetch.

candidates - The candidate selector.

exclude - The exclude selector.

Method Detail

createContext

public MeanAccumulator 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.

getPrefix

protected String getPrefix()

Description copied from class: AbstractMetric

A prefix to be applied to column names. If non-null, this prefix will be applied and separated with a period.

Overrides:

getPrefix in class AbstractMetric<MeanAccumulator,NDCGTopNMetric.Result,NDCGTopNMetric.Result>

Returns:

The prefix to apply to column names.

getSuffix

protected String getSuffix()

Description copied from class: AbstractMetric

A suffix to be applied to column names. If non-null, this suffix will be applied and separated with a period.

Overrides:

getSuffix in class AbstractMetric<MeanAccumulator,NDCGTopNMetric.Result,NDCGTopNMetric.Result>

Returns:

The suffix to apply to column names.

doMeasureUser

public NDCGTopNMetric.Result doMeasureUser(TestUser user,
                                           MeanAccumulator context)

Description copied from class: AbstractMetric

Measure a user with typed results.

Specified by:

doMeasureUser in class AbstractMetric<MeanAccumulator,NDCGTopNMetric.Result,NDCGTopNMetric.Result>

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 NDCGTopNMetric.Result getTypedResults(MeanAccumulator context)

Description copied from class: AbstractMetric

Get the typed results from an accumulator.

Specified by:

getTypedResults in class AbstractMetric<MeanAccumulator,NDCGTopNMetric.Result,NDCGTopNMetric.Result>

Parameters:

context - The context.

Returns:

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