org.grouplens.lenskit.eval.metrics.topn

Class TopNEntropyMetric

java.lang.Object

org.grouplens.lenskit.eval.metrics.AbstractMetric<TopNEntropyMetric.Context,TopNEntropyMetric.Result,Void>

org.grouplens.lenskit.eval.metrics.topn.TopNEntropyMetric

All Implemented Interfaces:

Closeable, AutoCloseable, Metric<TopNEntropyMetric.Context>

public class TopNEntropyMetric
extends AbstractMetric<TopNEntropyMetric.Context,TopNEntropyMetric.Result,Void>

Metric that measures the entropy of the top N recommendations across all users. This tell us essentially how large of a range of the items your recommender is covering. Small values indicate that the algorithm tends to prefer a small number of items which it recomments to all users. Large values mean that the algorithm recommends many different items (to many different users) The smallest value happens when the topN list is the same for all users (which would give an entropy of roughly log_2(N)). The largest value happens when each item is recommended the same number of times (for an entropy of roughly log_2(number of items)).

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	TopNEntropyMetric.Builder
class	TopNEntropyMetric.Context
static class	TopNEntropyMetric.Result

Constructor Summary

Constructors

Constructor and Description
TopNEntropyMetric(String pre, String sfx, int listSize, ItemSelector candidates, ItemSelector exclude)

Method Summary

Modifier and Type	Method and Description
TopNEntropyMetric.Context	createContext(Attributed algo, TTDataSet ds, Recommender rec) Create the context for an experimental condition (algorithm/data set pair).
Void	doMeasureUser(TestUser user, TopNEntropyMetric.Context 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 TopNEntropyMetric.Result	getTypedResults(TopNEntropyMetric.Context context) Get the typed results from an accumulator.
List<String>	getUserColumnLabels() Get labels for the per-user columns output by this evaluator.

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

close, getColumnLabels, getResults, measureUser

Methods inherited from class java.lang.Object

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

Constructor Detail

TopNEntropyMetric

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

Method Detail

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<TopNEntropyMetric.Context,TopNEntropyMetric.Result,Void>

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<TopNEntropyMetric.Context,TopNEntropyMetric.Result,Void>

Returns:

The suffix to apply to column names.

createContext

public TopNEntropyMetric.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.

getUserColumnLabels

public List<String> getUserColumnLabels()

Description copied from interface: Metric

Get labels for the per-user columns output by this evaluator.

Specified by:

getUserColumnLabels in interface Metric<TopNEntropyMetric.Context>

Overrides:

getUserColumnLabels in class AbstractMetric<TopNEntropyMetric.Context,TopNEntropyMetric.Result,Void>

Returns:

The labels for this evaluator's per-user output, used as column headers when outputting the results table.

See Also:

Metric.measureUser(TestUser, Object)

doMeasureUser

public Void doMeasureUser(TestUser user,
                          TopNEntropyMetric.Context context)

Description copied from class: AbstractMetric

Measure a user with typed results.

Specified by:

doMeasureUser in class AbstractMetric<TopNEntropyMetric.Context,TopNEntropyMetric.Result,Void>

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 TopNEntropyMetric.Result getTypedResults(TopNEntropyMetric.Context context)

Description copied from class: AbstractMetric

Get the typed results from an accumulator.

Specified by:

getTypedResults in class AbstractMetric<TopNEntropyMetric.Context,TopNEntropyMetric.Result,Void>

Parameters:

context - The context.

Returns:

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