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java.lang.Objectorg.apache.mahout.cf.taste.impl.similarity.AbstractItemSimilarity
org.apache.mahout.cf.taste.impl.similarity.CityBlockSimilarity
public final class CityBlockSimilarity
Implementation of City Block distance (also known as Manhattan distance) - the absolute value of the difference of each direction is summed. The resulting unbounded distance is then mapped between 0 and 1.
Constructor Summary | |
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CityBlockSimilarity(DataModel dataModel)
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Method Summary | |
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double[] |
itemSimilarities(long itemID1,
long[] itemID2s)
A bulk-get version of ItemSimilarity.itemSimilarity(long, long) . |
double |
itemSimilarity(long itemID1,
long itemID2)
Returns the degree of similarity, of two items, based on the preferences that users have expressed for the items. |
void |
refresh(Collection<Refreshable> alreadyRefreshed)
Triggers "refresh" -- whatever that means -- of the implementation. |
void |
setPreferenceInferrer(PreferenceInferrer inferrer)
Attaches a PreferenceInferrer to the UserSimilarity implementation. |
double |
userSimilarity(long userID1,
long userID2)
Returns the degree of similarity, of two users, based on the their preferences. |
Methods inherited from class org.apache.mahout.cf.taste.impl.similarity.AbstractItemSimilarity |
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allSimilarItemIDs, getDataModel |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public CityBlockSimilarity(DataModel dataModel)
Method Detail |
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public void setPreferenceInferrer(PreferenceInferrer inferrer)
UserSimilarity
Attaches a PreferenceInferrer
to the UserSimilarity
implementation.
setPreferenceInferrer
in interface UserSimilarity
inferrer
- PreferenceInferrer
UnsupportedOperationException
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.
refresh
in interface Refreshable
refresh
in class AbstractItemSimilarity
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 double itemSimilarity(long itemID1, long itemID2) throws TasteException
ItemSimilarity
Returns the degree of similarity, of two items, based on the preferences that users have expressed for the items.
itemSimilarity
in interface ItemSimilarity
itemID1
- first item IDitemID2
- second item ID
Double.NaN
similarity is unknown
NoSuchItemException
- if either item is known to be non-existent in the data
TasteException
- if an error occurs while accessing the datapublic double[] itemSimilarities(long itemID1, long[] itemID2s) throws TasteException
ItemSimilarity
A bulk-get version of ItemSimilarity.itemSimilarity(long, long)
.
itemSimilarities
in interface ItemSimilarity
itemID1
- first item IDitemID2s
- second item IDs to compute similarity with
NoSuchItemException
- if any item is known to be non-existent in the data
TasteException
- if an error occurs while accessing the datapublic double userSimilarity(long userID1, long userID2) throws TasteException
UserSimilarity
Returns the degree of similarity, of two users, based on the their preferences.
userSimilarity
in interface UserSimilarity
userID1
- first user IDuserID2
- second user ID
Double.NaN
similarity is unknown
NoSuchUserException
- if either user is known to be non-existent in the data
TasteException
- if an error occurs while accessing the data
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