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java.lang.Objectorg.apache.mahout.cf.taste.impl.recommender.AbstractRecommender
org.apache.mahout.cf.taste.impl.recommender.ItemUserAverageRecommender
public final class ItemUserAverageRecommender
Like ItemAverageRecommender
, except that estimated preferences are adjusted for the users' average
preference value. For example, say user X has not rated item Y. Item Y's average preference value is 3.5.
User X's average preference value is 4.2, and the average over all preference values is 4.0. User X prefers
items 0.2 higher on average, so, the estimated preference for user X, item Y is 3.5 + 0.2 = 3.7.
Constructor Summary | |
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ItemUserAverageRecommender(DataModel dataModel)
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Method Summary | |
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float |
estimatePreference(long userID,
long itemID)
|
List<RecommendedItem> |
recommend(long userID,
int howMany,
IDRescorer rescorer)
|
void |
refresh(Collection<Refreshable> alreadyRefreshed)
Triggers "refresh" -- whatever that means -- of the implementation. |
void |
removePreference(long userID,
long itemID)
Default implementation which just calls DataModel.removePreference(long, long) (Object, Object)}. |
void |
setPreference(long userID,
long itemID,
float value)
Default implementation which just calls DataModel.setPreference(long, long, float) . |
String |
toString()
|
Methods inherited from class org.apache.mahout.cf.taste.impl.recommender.AbstractRecommender |
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getAllOtherItems, getDataModel, getDefaultCandidateItemsStrategy, recommend |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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public ItemUserAverageRecommender(DataModel dataModel) throws TasteException
TasteException
Method Detail |
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public List<RecommendedItem> recommend(long userID, int howMany, IDRescorer rescorer) throws TasteException
userID
- user for which recommendations are to be computedhowMany
- desired number of recommendationsrescorer
- rescoring function to apply before final list of recommendations is determined
List
of recommended RecommendedItem
s, ordered from most strongly recommend to
least
TasteException
- if an error occurs while accessing the DataModel
public float estimatePreference(long userID, long itemID) throws TasteException
userID
- user ID whose preference is to be estimateditemID
- item ID to estimate preference for
Double.NaN
TasteException
- if an error occurs while accessing the DataModel
public void setPreference(long userID, long itemID, float value) throws TasteException
AbstractRecommender
Default implementation which just calls DataModel.setPreference(long, long, float)
.
setPreference
in interface Recommender
setPreference
in class AbstractRecommender
userID
- user to set preference foritemID
- item to set preference forvalue
- preference value
TasteException
- if an error occurs while accessing the DataModel
public void removePreference(long userID, long itemID) throws TasteException
AbstractRecommender
Default implementation which just calls DataModel.removePreference(long, long)
(Object, Object)}.
removePreference
in interface Recommender
removePreference
in class AbstractRecommender
userID
- user from which to remove preferenceitemID
- item for which to remove preference
TasteException
- if an error occurs while accessing the DataModel
public void refresh(Collection<Refreshable> alreadyRefreshed)
Refreshable
Triggers "refresh" -- whatever that means -- of the implementation. The general contract is that any
Refreshable
should always leave itself in a consistent, operational state, and that the refresh
atomically updates internal state from old to new.
alreadyRefreshed
- Refreshable
s that are known to have already been
refreshed as a result of an initial call to a Refreshable.refresh(Collection)
method on some
object. This ensure that objects in a refresh dependency graph aren't refreshed twice
needlessly.public String toString()
toString
in class Object
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