org.apache.mahout.cf.taste.impl.model

Class GenericDataModel

java.lang.Object

org.apache.mahout.cf.taste.impl.model.AbstractDataModel

org.apache.mahout.cf.taste.impl.model.GenericDataModel

All Implemented Interfaces:

Serializable, Refreshable, DataModel

public final class GenericDataModel
extends AbstractDataModel

A simple DataModel which uses a given List of users as its data source. This implementation is mostly useful for small experiments and is not recommended for contexts where performance is important.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
GenericDataModel(DataModel dataModel) Deprecated. without direct replacement. Consider toDataMap(DataModel) with GenericDataModel(FastByIDMap)
GenericDataModel(FastByIDMap<PreferenceArray> userData) Creates a new from the given users (and their preferences).
GenericDataModel(FastByIDMap<PreferenceArray> userData, FastByIDMap<FastByIDMap<Long>> timestamps) Creates a new from the given users (and their preferences).

Method Summary

Methods

Modifier and Type	Method and Description
LongPrimitiveArrayIterator	getItemIDs()
FastIDSet	getItemIDsFromUser(long userID)
int	getNumItems()
int	getNumUsers()
int	getNumUsersWithPreferenceFor(long itemID)
int	getNumUsersWithPreferenceFor(long itemID1, long itemID2)
PreferenceArray	getPreferencesForItem(long itemID)
PreferenceArray	getPreferencesFromUser(long userID)
Long	getPreferenceTime(long userID, long itemID) Retrieves the time at which a preference value from a user and item was set, if known.
Float	getPreferenceValue(long userID, long itemID) Retrieves the preference value for a single user and item.
FastByIDMap<PreferenceArray>	getRawItemData() This is used mostly internally to the framework, and shouldn't be relied upon otherwise.
FastByIDMap<PreferenceArray>	getRawUserData() This is used mostly internally to the framework, and shouldn't be relied upon otherwise.
LongPrimitiveArrayIterator	getUserIDs()
boolean	hasPreferenceValues()
void	refresh(Collection<Refreshable> alreadyRefreshed) Triggers "refresh" -- whatever that means -- of the implementation.
void	removePreference(long userID, long itemID) Removes a particular preference for a user.
void	setPreference(long userID, long itemID, float value) Sets a particular preference (item plus rating) for a user.
static FastByIDMap<PreferenceArray>	toDataMap(DataModel dataModel) Exports the simple user IDs and preferences in the data model.
static FastByIDMap<PreferenceArray>	toDataMap(FastByIDMap<Collection<Preference>> data, boolean byUser) Swaps, in-place, Lists for arrays in Map values .
String	toString()

Methods inherited from class org.apache.mahout.cf.taste.impl.model.AbstractDataModel

getMaxPreference, getMinPreference, setMaxPreference, setMinPreference

Methods inherited from class java.lang.Object

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

Constructor Detail

GenericDataModel

public GenericDataModel(FastByIDMap<PreferenceArray> userData)

Creates a new from the given users (and their preferences). This DataModel retains all this information in memory and is effectively immutable.

Parameters:

userData - users to include; (see also toDataMap(FastByIDMap, boolean))

GenericDataModel

public GenericDataModel(FastByIDMap<PreferenceArray> userData,
                FastByIDMap<FastByIDMap<Long>> timestamps)

Creates a new from the given users (and their preferences). This DataModel retains all this information in memory and is effectively immutable.

Parameters:

userData - users to include; (see also toDataMap(FastByIDMap, boolean))

timestamps - optionally, provided timestamps of preferences as milliseconds since the epoch. User IDs are mapped to maps of item IDs to Long timestamps.

GenericDataModel

@Deprecated
public GenericDataModel(DataModel dataModel)
                 throws TasteException

Deprecated. without direct replacement. Consider toDataMap(DataModel) with GenericDataModel(FastByIDMap)

Creates a new containing an immutable copy of the data from another given DataModel.

Parameters:

dataModel - DataModel to copy

Throws:

TasteException - if an error occurs while retrieving the other DataModel's users

Method Detail

toDataMap

public static FastByIDMap<PreferenceArray> toDataMap(FastByIDMap<Collection<Preference>> data,
                                     boolean byUser)

Swaps, in-place, Lists for arrays in Map values .

Returns:

input value

toDataMap

public static FastByIDMap<PreferenceArray> toDataMap(DataModel dataModel)
                                              throws TasteException

Exports the simple user IDs and preferences in the data model.

Returns:

a FastByIDMap mapping user IDs to PreferenceArrays representing that user's preferences

Throws:

TasteException

getRawUserData

public FastByIDMap<PreferenceArray> getRawUserData()

This is used mostly internally to the framework, and shouldn't be relied upon otherwise.

getRawItemData

public FastByIDMap<PreferenceArray> getRawItemData()

This is used mostly internally to the framework, and shouldn't be relied upon otherwise.

getUserIDs

public LongPrimitiveArrayIterator getUserIDs()

Returns:

all user IDs in the model, in order

getPreferencesFromUser

public PreferenceArray getPreferencesFromUser(long userID)
                                       throws NoSuchUserException

Parameters:

userID - ID of user to get prefs for

Returns:

user's preferences, ordered by item ID

Throws:

NoSuchUserException - if there is no such user

getItemIDsFromUser

public FastIDSet getItemIDsFromUser(long userID)
                             throws TasteException

Parameters:

userID - ID of user to get prefs for

Returns:

IDs of items user expresses a preference for

Throws:

NoSuchUserException - if the user does not exist

TasteException - if an error occurs while accessing the data

getItemIDs

public LongPrimitiveArrayIterator getItemIDs()

Returns:

a LongPrimitiveIterator of all item IDs in the model, in order

getPreferencesForItem

public PreferenceArray getPreferencesForItem(long itemID)
                                      throws NoSuchItemException

Parameters:

itemID - item ID

Returns:

all existing Preferences expressed for that item, ordered by user ID, as an array

Throws:

NoSuchItemException - if the item does not exist

getPreferenceValue

public Float getPreferenceValue(long userID,
                       long itemID)
                         throws TasteException

Description copied from interface: DataModel

Retrieves the preference value for a single user and item.

Parameters:

userID - user ID to get pref value from

itemID - item ID to get pref value for

Returns:

preference value from the given user for the given item or null if none exists

Throws:

NoSuchUserException - if the user does not exist

TasteException - if an error occurs while accessing the data

getPreferenceTime

public Long getPreferenceTime(long userID,
                     long itemID)
                       throws TasteException

Description copied from interface: DataModel

Retrieves the time at which a preference value from a user and item was set, if known. Time is expressed in the usual way, as a number of milliseconds since the epoch.

Parameters:

userID - user ID for preference in question

itemID - item ID for preference in question

Returns:

time at which preference was set or null if no preference exists or its time is not known

Throws:

NoSuchUserException - if the user does not exist

TasteException - if an error occurs while accessing the data

getNumItems

public int getNumItems()

Returns:

total number of items known to the model. This is generally the union of all items preferred by at least one user but could include more.

getNumUsers

public int getNumUsers()

Returns:

total number of users known to the model.

getNumUsersWithPreferenceFor

public int getNumUsersWithPreferenceFor(long itemID)

Parameters:

itemID - item ID to check for

Returns:

the number of users who have expressed a preference for the item

getNumUsersWithPreferenceFor

public int getNumUsersWithPreferenceFor(long itemID1,
                               long itemID2)

Parameters:

itemID1 - first item ID to check for

itemID2 - second item ID to check for

Returns:

the number of users who have expressed a preference for the items

removePreference

public void removePreference(long userID,
                    long itemID)

Description copied from interface: DataModel

Removes a particular preference for a user.

Parameters:

userID - user from which to remove preference

itemID - item to remove preference for

setPreference

public void setPreference(long userID,
                 long itemID,
                 float value)

Description copied from interface: DataModel

Sets a particular preference (item plus rating) for a user.

Parameters:

userID - user to set preference for

itemID - item to set preference for

value - preference value

refresh

public void refresh(Collection<Refreshable> alreadyRefreshed)

Description copied from interface: Refreshable

Triggers "refresh" -- whatever that means -- of the implementation. The general contract is that any should always leave itself in a consistent, operational state, and that the refresh atomically updates internal state from old to new.

Parameters:

alreadyRefreshed - s that are known to have already been refreshed as a result of an initial call to a method on some object. This ensure that objects in a refresh dependency graph aren't refreshed twice needlessly.

hasPreferenceValues

public boolean hasPreferenceValues()

Returns:

true iff this implementation actually stores and returns distinct preference values; that is, if it is not a 'boolean' DataModel

toString

public String toString()

Overrides:

toString in class Object